Apart from his role on Mad Men, Slattery has had roles such as union organizer Al Kahn on Homefront; Senator Walter Mondale in the HBO miniseries From the Earth to the Moon; as political adviser Tommy Flannigan in the HBO series K Street; guest appearances as Will Truman's brother Sam on Will & Grace; as Michael Cassidy, Amy's estranged husband, on Judging Amy; politician Bill Kelley on Sex and the City; principal Dennis Martino on Ed; and college president Peter Benedict on Jack and Bobby. In March 2007, he began a series of appearances on Desperate Housewives portraying Victor Lang, Gabrielle Solis's (Eva Longoria) second husband, until his character's death in Season 4. In December 2009, Slattery appeared on The Colbert Report in a faux commercial advertising gold.