Secor was born in Tacoma, Washington. He grew up in nearby Federal Way and graduated from Federal Way High School in 1975. His father worked in sales.

After working in several movies, including Heart of Dixie (1989), City Slickers (1991), Sleeping with the Enemy (1991), Delusion (1991), and Untamed Heart (1993), Secor was cast as Det. Tim Bayliss in the pilot of Homicide: Life on the Street in 1993, a role which he would fill for the entirety of the series. Throughout most of this time, Secor was paired on screen with actor Andre Braugher, who played his partner Det. Frank Pembleton. Though the show was an ensemble work, Secor's character was placed in a particularly pivotal role, as the series began its first episode on his first day of work in the Baltimore homicide unit, and ended the series finale with his resignation. Bayliss' character was conflicted through much of the show's run, obsessed with the murder of a Baltimore child he and Pembleton could not solve. The character also had issues involving social protest, past molestation by an uncle and questions about his own sexuality. In 1994, Kyle also played "Swoop" in the film Drop Zone starring Wesley Snipes.

After a successful seven-year run on Homicide, Secor went on to a short-lived role on Party of Five and made two feature films, Endsville and Beat. He returned to the small screen as a Doctor in the CBS production, City Of Angels, for 9 weeks during the fall of 2000. He appeared in the made-for-TV movie Bailey's Mistake, which was shown on ABC on March 18, 2001. He appeared in the pilot episode of Crossing Jordan in the fall of 2001 and had a recurring supporting role in the cancelled ABC production of Steven Bochco's Philly from September 2001 through May 2002. In fall 2002 he was seen as a guest star on CBS's Without A Trace. Spring of 2004 brought Lifetime's Infidelity opposite former Philly costar Kim Delaney, and the long-awaited Disney-ABC television film A Wrinkle In Time featuring him in the role of Hank. He had a recurring role as Jake Kane in the 2004–2005 freshman season of the show Veronica Mars and guest-starred in the series finale.

Secor married Actress Kari Coleman on January 28, 2002. They have two children, Emery and Harper.

From 2005 to 2006, he starred with Geena Davis in ABC's Commander in Chief, playing Rod Calloway, the husband of the female President. In 2007, he played Alan 'Skip' Matthews in the short-lived show Hidden Palms.

Secor had a recurring role as Hanson North, a defense attorney who has a romantic history with Laura Harris' character in ABC's Women's Murder Club, 2007 – 2008.

He also acted in Boston Legal as Dr. Robert L. Brooks who is married to Phoebe Prentice, a former flame of Alan Shore. Also, he guest starred in Ghost Whisperer as Doug Bancroft. In August 2010 he made a guest appearance on The Closer, as an airline pilot involved in drug smuggling. Secor appeared on the television series Hawaii Five-0 on the fifth episode of their first season, "Nalowale", playing Ambassador Michael Reeves.