Kaku was born in San Jose, California to Japanese immigrant parents. Reflecting on his childhood, he said: his grandfather had come to the United States to take part in the clean-up operation after the 1906 San Francisco Earthquake. His father was born in California, but received education in Japan, so spoke little English. Both his parents were put in the Tule Lake War Relocation Center, where they met and where his brother was born.

Kaku attended and played first board on the chess team of Cubberley High School in Palo Alto in the early 1960s. At the National Science Fair in Albuquerque, New Mexico, he attracted the attention of physicist Edward Teller, who took Kaku as a protégé, awarding him the Hertz Engineering Scholarship. Kaku graduated summa cum laude from Harvard University with a B.S. degree in 1968 and was first in his physics class. He attended the Berkeley Radiation Laboratory at the University of California, Berkeley and received a Ph.D. in 1972, and held a lectureship at Princeton University in 1973. During the Vietnam War, Kaku completed his US Army basic training at Fort Benning, Georgia and his advanced infantry training at Fort Lewis, Washington. However, the Vietnam War ended before he was deployed as an infantryman.

Kaku currently holds the Henry Semat Chair and Professorship in theoretical physics and a joint appointment at City College of New York, and the Graduate Center of the City University of New York, where he has lectured for more than 30 years. Presently, he is engaged in defining the "Theory of Everything", which seeks to unify the four fundamental forces of the universe: the strong force, the weak force, gravity and electromagnetism. He was a visiting professor at the Institute for Advanced Study in Princeton, and New York University. He is a Fellow of the American Physical Society. He is listed in Who's Who in Science and Engineering, and American Men and Women of Science.

He has published research articles on string theory from 1969 to 2000. In 1974, along with Prof. K. Kikkawa, he wrote the first paper on string field theory, now a major branch of string theory, which summarizes each of the five string theories into a single equation. In addition to his work on string field theory, he also authored some of the first papers on multi-loop amplitudes in string theory, the first paper on the divergences of these multi-loop amplitudes, the first paper on supersymmetry breaking at high temperatures in the early universe, the first paper on super-conformal gravity, and also some of the first papers on the non-polynomial closed string field theory. Many of the ideas he first explored have since blossomed into active areas of string research. His most recent research publication, on bosonic quantum membranes, was published in Physical Review in 2000.

Kaku is the author of several doctoral textbooks on string theory and quantum field theory and has published 170 articles in journals covering topics such as superstring theory, supergravity, supersymmetry, and hadronic physics. He is also author of the popular science books: Visions, Hyperspace, Einstein's Cosmos, and Parallel Worlds, and co-authored Beyond Einstein with Jennifer Thompson. Hyperspace was a best-seller and was voted one of the best science books of the year by both The New York Times and The Washington Post. Parallel Worlds was a finalist for the Samuel Johnson Prize for non-fiction in the UK.

In Physics of the Impossible, he examines the technologies of invisibility, teleportation, precognition, star ships, antimatter engines, time travel and more...all regarded as things that are not possible today but that might be possible in the future. In this book, he ranks these subjects according to when, if ever, these technologies might become reality. In March 2008, Physics of the Impossible entered the New York Times best-seller list, and stayed on for five weeks.

Kaku has publicly stated his concerns over matters including the human cause of global warming, nuclear armament, nuclear power and the general misuse of science. He was critical of the Cassini-Huygens space probe because of the 72 pounds of plutonium contained in the craft for use by its radioisotope thermoelectric generator. Conscious of the possibility of casualties if the probe's fuel were dispersed into the environment during a malfunction and crash as the probe was making a 'sling-shot' maneuver around earth, Kaku publicly criticized NASA's risk assessment. He has also spoken on the dangers of space junk and called for more and better monitoring. Kaku is generally a vigorous supporter of the exploration of outer space, believing that the ultimate destiny of the human race may lie in the stars; but he is critical of some of the cost-ineffective missions and methods of NASA.

Kaku credits his anti-nuclear war position to programs he heard on the Pacifica Radio network, during his student years in California. It was during this period that he made the decision to turn away from a career developing the next generation of nuclear weapons in association with Dr. Teller and focused on research, teaching, writing and media. Dr. Kaku joined with others such as Dr. Helen Caldicott, Jonathan Schell, Peace Action and was instrumental in building a global anti-nuclear weapons movement that arose in the 1980s, during the administration of US President Ronald Reagan.

Kaku was a board member of Peace Action and on the board of radio station WBAI-FM in New York City where he originated his long running program, Explorations, that focused on the issues of science, war, peace and the environment.

Kaku has appeared in many forms of media and on many programs and networks, including Good Morning America, The Screen Savers, Larry King Live, 60 Minutes, Nightline, 20/20, Naked Science, CNN, ABC News, CBS News, NBC News, Al Jazeera English, Fox News Channel, The History Channel, The Science Channel, The Discovery Channel, TLC, Countdown with Keith Olbermann, The Colbert Report, The Art Bell Show and its successor, Coast To Coast AM, BBC World News America, The Opie & Anthony Show and The Covino & Rich Show.

In 1999, Kaku was one of the scientists profiled in the feature-length film, Me and Isaac Newton, directed by Michael Apted. It played theatrically in the United States, was later broadcast on national TV, and won several film awards.

In 2005 Kaku appeared in the short documentary Obsessed & Scientific. The film is about the possibility of time travel and the people who dream about it. It screened at the Montreal World Film Festival and a feature film expansion is in development talks. Kaku also appeared in the ABC documentary UFOs: Seeing Is Believing, in which he suggested that while he believes it is extremely unlikely that extraterrestrials have ever actually visited Earth, we must keep our minds open to the possible existence of civilizations a million years ahead of us in technology, where entirely new avenues of physics open up. He also discussed the future of interstellar exploration and alien life in the Discovery Channel special Alien Planet as one of the multiple speakers who co-hosted the show, and Einstein's Theory of Relativity on The History Channel.

In February 2006, Kaku appeared as presenter in the BBC-TV four-part documentary Time which seeks to explore the mysterious nature of time. Part one of the series concerns personal time, and how we perceive and measure the passing of time. The second in the series deal with cheating time, exploring possibilities of extending the lifespan of organisms. The geological time covered in part three explores the ages of the earth and the sun. Part four covers the topics of cosmological time, the beginning of time and the events that occurred at the instant of the big bang.

On January 28, 2007, Kaku hosted the Discovery Channel series 2057. This three-hour program discussed how medicine, the city, and energy will change over the next 50 years. In 2008, Kaku hosted the three-hour BBC-TV documentary Visions of the Future, on the future of computers, medicine, and quantum physics, and appeared in several episodes of the History Channel's Universe series.

On Dec. 1, 2009, he began hosting a 12-episode weekly TV series for the Science Channel at 10 pm, called "Physics of the Impossible," based on his best-selling book. Each 30 minute episode discusses the scientific basis behind such imaginative schemes as: time travel, parallel universes, warp drive, star ships, light sabers, force fields, teleportation, invisibility, death stars, and even superpowers and flying saucers. Each episode includes interviews with the world's top scientists working on prototypes of these technologies, interviews with sci fi fans, clips from science fiction movies, and special effects and computer graphics. Although these inventions are impossible today, the series discusses when these technologies might become feasible in the future.

In 2010, He began to appear in a series on the website Gametrailers.com called 'Science of Games', discussing the scientific aspects of various popular video games such as Mass Effect 2 and Star Wars: The Force Unleashed.

Kaku is popular in mainstream media because of his knowledge and his accessible approach to presenting complex subjects in science. While his technical writings are confined to theoretical physics, his public speaking and media appearances cover a broad range of topics, from the Kardashev scale to more esoteric subjects such as wormholes and time travel. In January 2007, Kaku visited the Middle Eastern country of Oman. While there, he talked at length to select members of that country's decision makers. In an interview with local media, Dr Kaku elaborated on his vision of mankind's future. Kaku considers climate change and terrorism as serious threats in man's evolution from a Type 0 civilization to Type 1.

Kaku is the host of the weekly, one hour radio program Explorations, produced by the Pacifica Foundation's WBAI in New York. "Explorations" is syndicated to community and independent radio stations and makes previous broadcasts available on the program's website. Kaku defines the show as dealing with the general topics of science, war, peace and the environment.

In April 2006, Kaku began broadcasting Science Fantastic on 90 commercial radio stations, the only nationally syndicated science program on commercial radio in the United States. It is syndicated by Talk Radio Network and now reaches 130 radio stations, and America's Talk on XM. The program is formatted as a live listener call-in show, focusing on "futurology," which he defines as the future of science . Featured guests include Nobel laureates and top researchers on the topics of string theory, time travel, black holes, gene therapy, aging, space travel, artificial intelligence and SETI. Unfortunately, when Kaku is busy filming for television, Science Fantastic goes on hiatus. Sometimes for several months. Kaku is also a frequent guest on many programs where he is outspoken in all areas and issues he considers of importance, such as the program "Coast to Coast AM," where on 30 November 2007, he reaffirmed his belief that there is a 100 percent probability of extraterrestrial life in the universe.

Kaku has appeared on the Opie and Anthony show a number of times, discussing popular fiction such as Back to The Future, Lost, and the theories behind time-travel that these and other fictional entertainment focus on. Steven G. Spruill's novel The Janus Equation, which describes the time travel of a post-op transsexual mating with her past self and thereby becoming father and mother to her present self, prompted Dr. Kaku's comment: "Well, you're in deep doo doo if that happens."

Michio Kaku has written a large range of science books.

Physics of the Impossible

Physics of the Impossible is an exploration into the science people dream about. Kaku explores things that people think are quite impossible. This book is divided into three sections: Class I, Class II, and Class III, according to the time that the things he talks about might happen.

Hyperspace

Hyperspace is about the four forces of the universe and higher dimensions.

Parallel Worlds

Parallel Worlds talks about the possibilities of the existence of parallel worlds. Kaku also talks about black holes and other frequently asked matters of advanced physics.

Beyond Einstein

Beyond Einstein is a resource for people wanting to know more about physics. Kaku mostly talks about Einstein and his quest for the Theory of Everything.