Howard was born on March 28, 1944, in El Centro, California, the son of Martha Carey (née McDonald) and Kenneth Joseph Howard, a stockbroker,^[4][5] being the elder of their two sons. His younger brother, the late Don Howard, was also an actor and director.^[6][7] His approximately 6-foot 6-inch (1.98 m) stature earned him the nickname "Stork" as a high school student. He grew up in Manhasset, New York, on Long Island.^[8]

The nickname "The White Shadow" was given to him by the Long Island press in 1961, as, at age 17, Howard was the only white starter on the Manhasset High School varsity basketball team.^[9]

A member of the National Honor Society in high school, Howard turned down several offers of basketball scholarships in favor of a more focused academic education. He graduated in 1966 from Amherst College, where he served as captain of the basketball team.^[10] He was also a member of the a cappella singing group The Zumbyes. He attended Yale School of Drama but left to make his Broadway debut before completing his master's degree^[11] – which he achieved in 1999.

Howard began his career on Broadway in Promises, Promises with Jerry Orbach. In 1970, he won a Tony Award as Best Supporting or Featured Actor (Dramatic) for Child's Play. Howard later starred on Broadway as Thomas Jefferson in 1776 and reprised the role in the 1972 film. His other Broadway appearances included Seesaw in 1973 and The Norman Conquests. Howard portrayed several U.S. presidents in the 1975 Broadway musical 1600 Pennsylvania Avenue and appeared as Warren G. Harding in Camping with Henry and Tom in 1995.^[12] He appeared in legitimate theater in many cities, most recently as Tip O'Neill in a one-man show According to Tip, at the New Repertory Theatre in Watertown, Massachusetts.^[13]

On television, Howard appeared as Ken Reeves, a Los Angeles high school basketball coach, in The White Shadow, produced by Bruce Paltrow in 1978. Howard had the starring role in the 1973 TV series Adam's Rib opposite his good friend (and Paltrow's wife) Blythe Danner, who also played wife Martha to his Thomas Jefferson in the film version of 1776. He starred in The Manhunter, a crime drama that was part of CBS's lineup for the 1974–75 television season.

Howard starred in the TV movie Father Damien in 1980 (in which he replaced David Janssen in the title role after Janssen died a few days after the movie started production) and won a Daytime Emmy Award in 1981 for his performance as the ideal father in the CBS afternoon special The Body Human: Facts for Boys. Howard's additional credits included "Sidney Sheldon's Rage of Angels, 1983", the 2000 miniseries Perfect Murder, Perfect Town, and the feature film Dreamer: Inspired by a True Story, both co-starring Kris Kristofferson. He played the title character in the 1984 American Playhouse production of Mark Twain's Pudd'nhead Wilson, having earlier played Twain on Bonanza. Later, he appeared as Garrett Boydston in Dynasty and its spin-off The Colbys. In the early 1990s, he appeared on Murder, She Wrote and, from 2001–04, in Crossing Jordan as the title character's father. In 2007, he appeared in the Jimmy Smits series Cane.

Howard guest-starred on numerous television dramas. He was guest villain in Hart to Hart Returns, a 1993 made-for-TV movie. He also appeared in season one of The West Wing as President Bartlet's first choice for US Supreme Court Justice in the episode "The Short List". His other dramatic guest roles included NYPD Blue, The Practice, Boston Legal, Cold Case, Dirty Sexy Money, Eli Stone, Brothers and Sisters, Law & Order: Special Victims Unit, Curb Your Enthusiasm, Fairly Legal, Crossing Jordan, The Closer, Blue Bloods, The Golden Girls, The Office, and 30 Rock.

Howard made his movie debut in 1970, in Tell Me That You Love Me, Junie Moon, opposite Liza Minnelli. Numerous dramatic and comedic movie roles followed, including: Otto Preminger's Such Good Friends with Dyan Cannon and Jennifer O'Neill, 1776, The Strange Vengeance of Rosalie, Independence, Second Thoughts, Oscar with Sylvester Stallone in 1991, Ulterior Motives, Clear and Present Danger with Harrison Ford in 1994, The Net with Sandra Bullock in 1995, Tactical Assault, Dreamer: Inspired by a True Story, and In Her Shoes in 2005.

In 2007, Howard appeared again with Stallone in Rambo, and in George Clooney's Michael Clayton. In 2010, he starred in The Numbers Game with Steven Bauer. He next appeared as Harlan F. Stone in Clint Eastwood's J. Edgar.

He gave an acclaimed performance as Phelan Beale in the 2009 HBO film Grey Gardens, playing opposite Jessica Lange, for which he received an Emmy Award.^[14] His last films were Better Living Through Chemistry (2013), A.C.O.D.(2013), The Judge (2014), The Wedding Ringer (2015) and the biographical comedy-drama film Joy (2015).

Ken Howard was elected the National President of the Screen Actors Guild on September 24, 2009.

Howard was the author of the 2003 book Act Natural: How to Speak to Any Audience,^[15] based on the drama courses he had taught at Harvard University. He was a popular reader for audiobooks.^[3]

Howard was married three times. His first wife was actress Louise Sorel (m. 1973–75). His second wife was writer and advice columnist Margo Lederer (m. 1977–91). His final marriage was to stuntwoman Linda Fetters Howard (m. 1992–2016).^[16]

In 2000, Howard underwent a kidney transplant; the donor was family friend Jeannie Epper,^[17] with whom Linda had worked in the stunt community.^[18]

In 2007, Howard was diagnosed with stage four prostate cancer. In March 2016, he was hospitalized in Valencia, California, with shingles, where he died on March 23, five days before his 72nd birthday.^[19] He was the first and, as of 2024^[update], the only Screen Actors Guild or SAG-AFTRA national president to die in office.

George Clooney, in whose 2007 legal thriller, Michael Clayton, Howard appeared, remembered having met him for the first time, in 1983 at 20th Century Fox, as a fan of The White Shadow.^[20]

• Ken Howard at the Internet Broadway Database  
• Ken Howard at the Internet Off-Broadway Database
• Ken Howard at IMDb
• Variety Profile