Adams served in the United States Marine Corps during the Korean War as a combat photographer. One of his assignments was to photograph the entire Demilitarized Zone from end to end immediately following the war. This took him over a month to complete.

It was while covering the Vietnam War for the Associated Press that he took his best-known photograph – the picture of police chief General Nguy?n Ng?c Loan executing a Vietcong prisoner, Nguy?n V?n Lém, on a Saigon street, on February 1, 1968, during the opening stages of the Tet Offensive.

Adams won the 1969 Pulitzer Prize for Spot News Photography and a World Press Photo award for the photograph (captioned 'General Nguyen Ngoc Loan executing a Viet Cong prisoner in Saigon'), but would later lament its notoriety.

On Nguyen Ngoc Loan and his famous photograph, Adams wrote in Time:

Adams later apologized in person to General Nguyen and his family for the irreparable damage it did to the General's honor while he was alive. When Nguyen died, Adams praised him as a "hero" of a "just cause". On the television show "War Stories with Oliver North" Adams called Gen. Nguyen "a goddamned hero!"

He once said, "I would have rather been known more for the series of photographs I shot of 48 Vietnamese refugees who managed to sail to Thailand in a 30-foot boat, only to be towed back to the open seas by Thai marines." The photographs, and accompanying reports, helped persuade then President Jimmy Carter to grant the nearly 200,000 Vietnamese boat people asylum. He won the Robert Capa Gold Medal from the Overseas Press Club in 1977 for this series of photographs in his photo essay, "The Boat of No Smiles" (Published by AP) . Adams remarked, "It did some good and nobody got hurt."

Along with the Pulitzer, Adams received over 500 awards, including the George Polk Award for News Photography in 1968, 1977 and 1978, and numerous awards from World Press Photo, NPPA, Sigma Delta Chi, Overseas Press Club, and many other organizations.

Adams died in New York City from complications of amyotrophic lateral sclerosis, also known as Lou Gehrig's disease. Adams's legacy is continued through Barnstorm: The Eddie Adams Workshop, the photography workshop he started in 1988.

He is the subject of a 2009 documentary feature, An Unlikely Weapon, directed by Susan Morgan Cooper and narrated by Kiefer Sutherland.

The photographic archive of Eddie Adams has been donated by his widow, Alyssa Adams, to the Dolph Briscoe Center for American History at The University of Texas at Austin. The archive documents Adams's career and includes "Saigon Execution," his Pulitzer Prize-winning photograph. Measuring 200 linear feet in size, the Eddie Adams Photographic Archive includes slides, negatives, prints, audio and video materials, news stories, diaries, notes and tear sheets. In addition to substantive coverage of the Vietnam War, the collection includes his in-depth features on poverty in America, the homeless, Mother Teresa, Brazil, alternative society, anti-war demonstrations, and riots, as well as his intimate portraits of such high-profile figures as Ronald Reagan, Fidel Castro, Malcolm X, Clint Eastwood, Bette Davis, Bill Cosby, and Jerry Lewis.

On October 22, 2009 Swann Galleries auctioned a special print of Adams's most well-known image, Saigon (General Nguyen Ngoc Loan executing a Viet Cong prisoner Nguyen Van Lém). The oversize silver print image...printed in the 1980s...had been a gift to Adams’s son and came with letter of provenance. The back of the photograph was signed and had Adams's notation, "Saigon, 1968." It sold for $43,200.