First TV appearance was as a college senior on "The Dating Game" (1965) in 1967 and then a second time (date unknown at this time). Incredibly, he lost both times. Soon after, he appeared in TV commercials for products such as Pepsi-Cola.
Has played a Private Investigator in two TV series; Lance White in "The Rockford Files" (1974) and Thomas Magnum in "Magnum, P.I." (1980).
Another rare appearance without his trademark mustache was on "Charlie's Angels: Target: Angels (#1.5)" (1976), original air date 27 October 1976.
Was turned down for the lead role in the TV show "Vega$" (1978), which went to Robert Urich. Selleck and Urich once co-starred in a TV pilot (that was never picked up) called Bunco (1977) (TV).
Starred in six failed TV pilots before landing his breakthrough role in "Magnum, P.I." (1980).
"Magnum, P.I." (1980) named the the number one detective series of all time by "The Sleuth" TV Network.
Best known for his role on TV as the title character on "Magnum, P.I." (1980).
Selleck was originally cast as "Indiana Jones", but was not able to take the role because he was committed to "Magnum, P.I." (1980). "Magnum" did an episode, "Magnum, P.I.: Legend of the Lost Art (#8.10)" (1988), that parodied "Raiders", complete with hat, whip and booby traps.
For the 8th and final season of "Magnum, P.I." (1980), Universal Studios gave him a bonus of $350,000, which he spent on lavish gifts, such as Rolex watches, Porsches, $1000 bonuses, for the entire cast and crew of "Magnum, P.I." (1980).
The decision of choosing the leading role of Indiana Jones in Raiders of the Lost Ark (1981) or "Magnum, P.I." (1980) actually haunted Selleck so much that he consulted his best friend. Together they came to the conclusion that honoring his contract with "Magnum, P.I." (1980) was the honorable thing to do. It turned out that the shooting of the pilot for "Magnum, P.I." (1980) was delayed for over 6 months, which would have enabled Selleck to complete the role of Indiana Jones. Ironically, while waiting in Hawaii for "Magnum, P.I." (1980) to commence filming, Steven Spielberg and George Lucas were also in Hawaii to shoot scenes for Raiders of the Lost Ark (1981).
Was asked to star opposite Julie Andrews in Victor Victoria (1982) but hesitated, and by the time he decided he wanted the part, he was already locked into his "Magnum, P.I." (1980) contract - the very same contract that cost him the role of Indiana Jones in Raiders of the Lost Ark (1981).
While preparing for Mr. Baseball (1992), he joined the Detroit Tigers in 1992 for spring training. He actually took an at-bat (as a pinch hitter) in a game against the Cincinnati Reds, facing Reds' pitcher Tim Layana. Selleck ended up striking out after fouling away half a dozen pitches.
In the early Nineties Selleck shot a commercial for the conservative National Review. But in 1992 he made a $1,000 donation to the presidential bid of Democratic Senator Paul Tsongas. Five years later, New York Times columnist Maureen Dowd reported that Republicans were urging Selleck to run for the Senate in California - a story Selleck quickly shot down. His political profile has been low ever since. However, in 1999 he filmed an advertisement for the National Rifle Association. "He's not a Republican," says an actor who knows him. "He's an independent.".
When he "won" a Worst Supporting Actor Razzie® Award for his role in Christopher Columbus: The Discovery (1992), Selleck became one of the first stars, ever, to accept the $4.97 dis-honor. A video clip of him accepting it on "The Chevy Chase Show" (1993) can be seen at the Razzie YouTube channel (http://www.youtube.com/watch?v=a2HyToVfopY&feature=channel_video_title).
During the brief run of the late night "The Chevy Chase Show" (1993) on Fox, he guest-starred and, as a gag, asked to be presented his 1993 Worst Supporting Actor "Razzie" award for his performance as "King Ferdinand of Spain" in Christopher Columbus: The Discovery (1992). When the Razzie was actually presented to him on the air, Selleck took it in stride and asked the entire studio audience to "blow me a raspberry". Selleck thus became the third person in Razzie history to voluntarily accept one of the Worst Achievements in Film statuettes.
Is a member of the National Rifle Association and memorably sparred with Rosie O'Donnell on "The Rosie O'Donnell Show" (1996) about gun control and an advertisement in which he appeared supporting the NRA.
Shaved off his trademark moustache for the 1997 film In & Out (1997). Once rarely seen without it, he has since kept it off for most of his stage and screen work.
Honored by the Congressional Award in Washington, DC with the 1997 Horizon Award. The Horizon Award is a special recognition from the Joint Leadership of the United States Congress and the Congressional Award Board of Directors. The Horizon Award is presented to individuals from the private sectors who have contributed to expanding opportunities for all Americans through their own personal contributions, and who have set exceptional examples for young people through their successes in life.
Received an honorary doctorate from Pepperdine University. He was chosen because of his outstanding character and ethic. He is a board member of the non-profit Michael Josephson Institute of Ethics and co-founder of the Character Counts Coalition. Attended the University of Southern California and in his senior year earned a basketball scholarship after walking onto the team as a junior. [28 April 2000]
Turned down the role of Richard on the TV show "Titans" (2000).
In 2001, he appeared in the Broadway show "A Thousand Clowns" without a mustache, a rarity for Selleck. Unfortunately, the show was forced to close early due to 9/11.
Was considered as the next President of the National Rifle Association (NRA) following the retirement of his close friend Charlton Heston in 2003.
Publicly endorsed Senator John McCain in the 2008 presidential election.
He and his family maintain their primary residence in Thousand Oaks, California, but also have secondary properties in Freedom, California; Jonesboro, Maine; and in the Shetland Islands, located off Scotland. 
Although he plays Len Cariou's son in "Blue Bloods" (2010), he is only 5 years his junior in real life.
Vocally supported President Ronald Reagan throughout the 1980s. In "Blue Bloods" (2010), his character, "Commissioner Frank Reagan", has political ties.