Born into a large family in Boston, MA on Aug. 13, 1962, Slattery received his bachelor of fine arts from the Catholic University of America in 1984 before launching his acting career in the late 1980s. He traveled to Yugoslavia to play a convicted forger in the short-lived television version of "Dirty Dozen: The Series" (Fox, 1987-1990) before trekking back to the States for his theater debut opposite Nathan Lane in Terrance McNally's "The Lisbon Traviata" (1989). Attempts to find a regular television gig were largely fruitless; the spy drama "Under Cover" (ABC, 1990-91) was quashed after only a month due to real-life tensions in the Middle East, while the World War II-era drama "Homefront" (ABC, 1991-93) afforded him a meaty character in tough union organizer Al Kahn. But weak ratings sealed that show's fate. Slattery kept busy, however, landing guest spots on television and supporting roles in films like "Eraser" (1996) and "Sleepers" (1997). But Slattery found more rewarding work on the New York stage, making his Broadway debut as a comedy writer based on Larry Gelbart in Neil Simon's acclaimed "Laughter on the 23rd Floor" (1993). Slattery then enjoyed several collaborations with playwright Richard Greenberg, including "Night and Her Stars," playing Charles Van Doren of 1950s quiz show scandal fame, and "Three Days of Rain" (1997), in which he played both a father and his own son.In 1998, there was a revived interest in Slattery on the small screen, where he began to enjoy solid, attention-worthy parts on several top-rated and critically acclaimed shows. Supporting turns in the miniseries "A Woman of Independent Means" (1995) and the Hallmark Hall of Fame's adaptation of Horton Foote's "Lily Dale" (1996) preceded his appearance as Sam Truman, estranged brother to Eric McCormack's Will and eventual one-night stand of Grace (Debra Messing), in the first season of "Will and Grace." He then enjoyed two appearances as a politician with a particularly kinky fetish who dates Carrie (Sarah Jessica Parker) on "Sex and the City" in an episode aired in 2000. Both shows afforded him considerable exposure to a wider audience, as did a recurring role on the cult favorite "Ed," playing Dennis Martino, a humorless principal who steals away Carol Vessey (Julie Bowen), the love of hero Ed Stevens' (Thomas Cavanaugh) life, only to leave her at the altar at the end of the season. Slattery's icy performance as Martino cemented his frequent onscreen persona as the no-nonsense, taciturn antagonist, though he later proved effective as a romantic figure, most notably in the short-lived comedy series, "Maggie" (Lifetime, 1998-99), and the made-for-TV movie "Catch a Falling Star" (2000), where he played a blue collar worker who falls for a glamorous actress (Sela Ward). The buzz surrounding Slattery's television appearances eventually brought him back to features, where he enjoyed solid supporting turns in Steven Soderbergh's "Traffic" (2000), Thomas McCarthy's "The Station Agent" (2003) and Mike Newell's "Mona Lisa Smile" (2003). Soderbergh lured him back to television to play a troubled aide to real-life political consultant James Carville (as himself) in the lauded, but short-lived quasi-drama "K Street" (HBO, 2003-04). Though well-received by critics, the show proved too insider-ish for a mass audience and vanished after a handful of episodes. Slattery then played a college president for the highly publicized "Jack and Bobby" (The WB, 2004-05), which also suffered from a fatal dose of low ratings. Slattery moved on to a string of diverse supporting roles in features ranging from a sympathetic handler for the Iwo Jima flag raisers in Clint Eastwood's "Flags of Our Fathers" (2006) to a decidedly unlikable CIA boss in "Charlie Wilson's War" (2007), followed by playing the mayor of a city under siege by Peter Dinklage's super villain in "Underdog" (2007). Slattery returned to the Broadway stage on several occasions during this period, most notably as a grief-stricken father in David Linsday-Abaire's Tony- and Pulitzer Prize-winning "Rabbit Hole" (2006). In the production, Slattery's real-life son provided the voice of his character's child in several home movies screened during the course of the play. Then in 2007, Slattery enjoyed a recurring role on "Desperate Housewives" as Victor Lang, a calculating politician who woos and eventually weds Gabriella (Evan Longoria Parker), only to discover that she was carrying on with ex-husband Carlos (Ricardo Antonio Chavira). Slattery shared a Screen Actors Guild nomination with his fellow "Housewives" in 2008. That same year, Slattery joined the cast of AMC's first scripted drama, "Mad Men," which explored the lives of Madison Avenue advertising executives at a major New York firm in the early 1960s. His character, Roger Sterling, seemed to personify the show's depiction of ad men as hard-living, misogynistic, shoot-from-the-hip types. A former Navy man with a wealth of war stories, Sterling enjoyed the privileges afforded to partners at the agency, Sterling Cooper, but eventually went overboard in his pursuit of the good life. The character would have been unbearable were it not for a degree of regret and casual humor injected by Slattery and the writers. Sterling instead became a tragicomic figure; one to be pitied as much as feared or admired. While continuing his work on "Mad Men," Slattery took advantage of film opportunities, including roles in the Philip K. Dick adaptation "The Adjustment Bureau" (2011) and the quiet dramas "In Our Nature" (2012) and "Bluebird" (2013). As the series wound down, Slattery began to explore his comic side with supporting roles in acclaimed series like "Arrested Development" (Netflix 2013), "Wet Hot American Summer: First Day At Camp" (Netflix 2015), and Fred Armisen and Bill Hader's "Documentary Now" (IFC 2015-). Slattery also appeared again as Howard Stark in the Paul Rudd-starring Marvel Universe caper "Ant-Man" (2015).