Memorable guest appearances on sitcoms followed, with Campos' dark good looks and fluency with several foreign accents (although his own English is flawless, having spoken it since the age of five) leading to roles including a part as macho Luis' gay brother on "Suddenly Susan" (NBC, 1997) and Zoe's lecherous Italian paramour on "Cybill" (CBS, 1998). He also had a guest starring role on the short-lived sitcom "Chicago Sons" (NBC, 1997) and was featured in the CBS miniseries "Mario Puzo's The Last Don" (also 1997) before taking on his first regular role on "Jesse". As Chilean-born Diego, Campos not only added an wordly and artistic flair to the sitcom's blue collar Buffalo, New York setting, he also emerged as a remarkably romantic and honest character, winning the admiration of many an audience member as he won the heart of the spunky no-nonsense title character. Campos' popularity didn't go unnoticed, and when the show underwent restructuring for its second season (1999-2000), Diego was one of the few regulars to make the cut, though the show ultimatley folded
Campos continued to find steady work on series television, appearing in the brief Showtime drama "Leap Years" (2001-2002) as an up-and-coming young lawyer, part of five friends living in New York watch their friendships and relationships evolve through three different eras: 1993, 2001 and 2008. There were also recurring roles on the Showtime series "Resurrection Blvd." in 2001 and as Dr. Eddie Dorset on the long-running medical drama "ER" in 2003, as well as a co-starring stint opposite Steven Weber on the short-lived ABC legal drama "The D.A." in 2004. After a guest spot as the facial/cranial plastic surgery specialist Quentin Costa on the juicy FX melodrama "Nip/Tuck" in 2004, Campos was added to the cast as a regular during the third season in 2005.