Reynolds was born in Corcoran, California, the eldest of three children of Verne and Pauline Reynolds; his father was the Socialist Labor Party's Vice-Presidential candidate in 1924, and its Presidential candidate on two occasions, in 1928 and 1932, and his son was in turn an active supporter of the SLP, many of his stories using SLP jargon such as 'Industrial Feudalism', and most dealing in some way with economic issues. The young Dallas accompanied his father on his speaking tours during his candidacies.

In 1935, while still in high school, Reynolds joined the Socialist Labor Party and became an active advocate of the party’s goals. The following year he toured the country with his father giving lectures and speeches, and became recognized as a significant force in advocating the SLP.

After graduating from high school in Kingston, New York, Reynolds worked on various newspapers in the area, progressing from reporter to editor, from 1936 to the early 1940s, in 1943 becoming a supervisor for IBM. He married Evelyn Sandell in 1937, with whom he had three children, Emil, LaVerne, and Dallas Jr.

From 1940 to 1943 Reynolds and his father toured the US as the chief team of spokesmen for the SLP. In 1944, feeling that it was his duty, Reynolds joined the US Army Transportation Corps and was stationed in the Phillipines as a ship's navigator.

When he left the service and returned home, Reynolds divorced Evelyn. His first fiction sale was in 1946, to Esquire magazine. In September 1947 he remarried, to Helen Jeanette Wooley, and two years later they moved to Taos, New Mexico, where Fredric Brown, his frequent collaborator, convinced Reynolds to try his hand at writing science fiction. His first sale of a science fiction story was "The Galactic Ghost", sold to Planet Stories in 1949, although not printed until 1954. His career soon took off, resulting in a sale of 17 stories in 1950 alone.

Reynolds made his home primarily in San Miguel de Allende, in Guanajuato, Mexico, from the early 1950s to his death in San Luis Potosi, Mexico. In the 1950s, he worked as the travel editor for men's magazine Rogue and traveled all over the world, visiting and living for periods in such places as Greece, Yugoslavia, Spain, Eastern Europe, Gibraltar, and North Africa.

Several of his last books are credited as co-authored with Dean Ing. When Reynolds knew he had a brief time to live, he tried to write enough to provide an income for his wife after his passing. To this end, he wrote as many novel outlines as he could, with the arrangement that Ing would finish them.

Most of Reynolds' stories took place in Utopian societies, many of which fulfilled L. L. Zamenhof's dream of Esperanto used worldwide as a universal second language. His novels predicted many things which have come to pass, including pocket computers and a worldwide computer network with information available at one's fingertips.

Many of his novels were written within the context of a highly mobile society in which few people maintained a fixed residence, leading to "mobile voting" laws which allowed someone living out of the equivalent of a motor home to vote when and where they chose.

Reynolds was also the first author to write an original novel based upon the 1966-1969 NBC television series Star Trek. The book, Mission to Horatius (1968), was aimed at young readers. In 1972, he used the name 'Maxine Reynolds' on two romantic suspense novels, House in the Kasbah and Home of the Inquisitor.

Novels

• The Case of the Little Green Men, 1951
• Mercenary From Tomorrow, 1962 (first book of the "Joe Mauser" series)
• The Earth War, 1963 (second book of the "Joe Mauser" series)
• Sweet Dreams, Sweet Princes; also known as Time Gladiator, 1964 (third book of the "Joe Mauser" series)
• Space Pioneer, 1965
• Planetary Agent X, 1965 (first book of the "United Planets" series)
• Dawnman Planet, 1966 (second book of the "United Planets" series)
• Of Godlike Power, 1966 (also known as Earth Unaware)
• The Rival Rigelians and Planetary Agent X, 1967 (third book of the "United Planets" series)
• After Some Tomorrow, 1967
• Code Duello, 1968 (fourth book of the "United Planets" series)
• The Cosmic Eye, 1969
• Computer War, 1969
• The Space Barbarians, 1969
• The Five Way Secret Agent, 1969
• Computer World, 1970
• Once Departed, 1970
• Black Man's Burden, 1972 (first book of the "North Africa" series)
• Border, Breed, Nor Birth, 1972 (second book of the "North Africa" series)
• Looking Backward from the Year 2000, 1973 (first book of the "Julian West" series)
• Depression or Bust and Dawnman Planet, 1974 (Parts were published previously titled "Depression. . .or Bust, "Expediter", and "Fad" in Analog magazine and titled "The Expert" in The Magazine of Fantasy and Science Fiction.)('Dawnman Planet' is a reprint of the second "United Planets - Section G" book)
• Commune 2000 A.D., 1974 (first book of the "Bat Hardin" series)
• The Towers of Utopia, 1975 (second book of the "Bat Hardin" series)
• Satellite City, 1975
• Amazon Planet, 1975 (fifth book of the "United Planets" series)
• The Cosmic Eye, 1975
• Ability Quotient, 1975
• Tomorrow Might Be Different, 1975
• Day After Tomorrow, 1976 (originally in Analog titled: "Status Quo")
• Section G: United Planets, 1976 (sixth book of the "United Planets" series)
• Rolltown, 1976 (third book of the "Bat Hardin" series)
• Galactic Medal of Honor, 1976
• After Utopia, 1977
• Perchance to Dream, 1977
• Space Visitor, 1977
• Police Patrol: 2000 A.D., 1977
• Equality in the Year 2000, 1977 (second book of the "Julian West" series)
• Trample an Empire Down, 1978
• The Best Ye Breed, 1978 (third book of the "North Africa" series)
• Brain World, 1978 (seventh book of the "United Planets" series)
• The Fracas Factor, 1978 (fourth book of the "Joe Mauser" series)
• Earth Unaware, 1979
• Lagrange Five, 1979 (first book of the "L-5 Community" series)
• The Lagrangists, 1983 (the second book of the "L-5 Community" series)
• Chaos in Lagrangia, 1984 (the third book of the "L-5 Community" series)
• Eternity (1984) (with Dean Ing)
• Home, Sweet Home 2010 A. D., 1984 (with Dean Ing)
• The Other Time, 1984 (with Dean Ing)
• Space Search, 1984
• Trojan Orbit, 1985 (with Dean Ing)
• Deathwish World, 1986 (with Dean Ing)

Collections

• The Best of Mack Reynolds, 1976
• Compounded Interests, 1983

Series contributed to

• Star Trek - Mission to Horatius, 1968

Anthologies edited

• Science Fiction Carnival, 1953 (with Fredric Brown)

Anthologies containing stories by Mack Reynolds

• New Worlds for Old, 1953
• Science Fiction Carnival, 1953
• A Century of Science Fiction, 1962
• Fifty Short Science Fiction Tales, 1963
• Venture Science Fiction 9, 1964
• The Unfriendly Future, 1965
• The Weird Ones, 1965
• The Magazine of Fantasy and Science Fiction 190, 1967
• The Playboy Book of Horror and the Supernatural, 1967
• Science Fiction Horizons No. 1, 1968
• The War Book, 1969
• 14 Great Tales of ESP, 1969
• The Year's Best Science Fiction 2, 1969
• Analog 7, 1970
• The John W Campbell Memorial Anthology, 1973
• Nova 3, 1973
• Study War No More, 1977 (Joe Halemann, Editor)
• Science Fiction of the Fifties, 1979
• 100 Great Fantasy Short Short Stories, 1984
• Mercenaries of Tomorrow, 1985
• Terrorists of Tomorrow, 1985
• Supernatural Sleuths, 1996
• Time Machines: The Best Time Travel Stories Ever Written, 1997
• Future War, 1999

Short stories

• The Martians and the Coys, 1948
• Isolationist, 1950 (reprinted in Fantastic, Oct. 1969)
• The Devil Finds Work, 1950
• Long Beer, Short Horn, Fantastic adventures (Nov. 1950)
• Six-Legged Svengali (with Frederic Brown), Worlds Beyond (Dec. 1950)
• Dark Interlude, (with Fredric Brown), Galaxy (Jan. 1951)
• The Joke Cartoonist, 1951 (with Fredric Brown) aka Garrigan's BEMs
• The Business, as Usual, 1952
• Me and Flapjack and the Martians, 1952 (with Fredric Brown)
• Your Soul Comes C.O.D., 1952
• No Return from Elba, Fantastic (Sept. 1953)
• The Adventure of the Ball of Nostradamus (with August Derleth), Magazine of Fantasy and Science Fiction (June 1955)
• Burnt Toast, 1955
• Compounded Interest, Magazine of Fantasy and Science Fiction (Aug. 1956)
• Snafu on the New Taos, 1957
• Obedience Guaranteed, Space Science Fiction Magazine (Spring 1957)
• Unborn Tomorrow, Astounding (June 1959)
• The Hunted Ones, Science Fiction Stories (Nov. 1959)
• I'm a Stranger Here Myself, 1960
• Russkies Go Home!, 1960
• Summit, Astounding (Feb. 1960)
• Revolution, Astounding (May 1960)
• Adaptation (short novel), Astounding (Aug. 1960)
• Combat, Analog (Oct. 1960)
• Gun for hire, Analog (Dec. 1960)
• Freedom, Analog (Feb. 1961)
• Ultima Thule (short novel), Analog (Mar. 1961)
• Farmer, Galaxy (June 1961)
• Status Quo (short novel), Analog (Aug. 1961) - Hugo (nominee)
• Black Man's Burden (two part serial), Analog (Dec. 1961-Jan. 1962)
• Earthlings Go Home, 1962
• Mercenary, 1962
• Good Indian, Analog (Sept. 1962)
• Subversive, Analog (Dec. 1962)
• Frigid Fracas (two part serial), Analog (Mar.-Apr. 1963)
• Expediter, Analog (May 1963)
• Spaceman on a Spree, Worlds of Tomorrow (June 1963)
• Pacifist, 1963 - appeared in the anthology The War Book (edited by James Sallis, 1969).
• Genus traitor, Analog (Aug. 1964)
• Sweet Dreams, Sweet Prince (three part serial), Analog (Nov. 1965-Jan. 1965)
• Fad, Analog (Apr. 1965)
• The Adventure of the Extraterrestrial, Analog (July 1965) - Nebula (nominee)
• Of Godlike Powers (two part serial), Worlds of Tomorrow (July-Aug. 1965)
• Space pioneer (three part serial), Analog (Sept.-Nov. 1965)
• A Leader for Yesteryear, If (Oct. 1965) - Nebula (nominee)
• Last of a Noble Breed, Worlds of Tomorrow (Nov. 1965)
• Time of War, If, (Nov. 1965)
• The Switcheroo Revisited, Analog (Feb. 1966)
• Your Soul Comes C.O.D., Fantastic (Mar. 1966)
• Survivor, Analog (July 1966)
• Arena, If (Sept. 1966)
• Amazon Planet (three part serial), Analog (Dec. 1966-Feb. 1967)
• Relic, Magazine of Fantasy and Science Fiction (Mar. 1967)
• The Enemy Within, Analog (Apr. 1967)
• The Throwaway Age, Worlds of Tomorrow (May 1967)
• Computer War (two part serial), Analog (June-July 1967)
• Depression or Bust, Analog (Aug. 1967)
• Fiesta Brava (short novel), Analog (Sept. 1967)
• Coup, Analog (Nov. 1967)
• Psi Assassin, Analog (Dec. 1967)
• Criminal in Utopia, 1968
• Extortion, Inc., Analog (Feb. 1969)
• The Five Way Secret Agent (two part serial), Analog (Apr.-May 1969)
• Black Sheep Astray, 1973
• The Cold War...Continued, 1973
• Hell's Fire, 1980 (with Gary Jennings)
• Golden Rule, Analog (Mar. 1980)
• What the Vintners Buy, Analog (Sept. 1980)
• The Union Forever, Analog (Dec. 1980)