At the insistence of his father (who wanted Rachins to go into the family business of food preparation), he studied business at the Wharton School of Finance but left after two years to pursue a career in acting. His acting studies with such well-known teachers as William Ball, Kim Stanley and Harvey Lembeck apparently paid off, as he soon landed a small role on Broadway in the short-lived "After the Rain" (1967) and later in "Hadrian VII" (1969). Later that year, he joined the original ensemble cast of the erotic revue "Oh! Calcutta!". Rachins has always professed to be shy, which made his appearance in this controversial, long-running sexual romp seem an odd choice of vehicle, as nudity was required in some of the show's sketches.

Moving to L.A., he accepted a fellowship at the American Film Institute, studying screenwriting and directing. As a result of his training, Rachins undertook a variety of TV jobs: writing for several episodic TV dramas, such as "Hart to Hart" (ABC) and "Hill Street Blues" (NBC); directing an episode of "Paris" (CBS); making guest appearances on such drama series as "J.J. Starbuck" (NBC) and the comedic "D.C. Follies" (syndicated); and acting in the TV-movie "Fear on Trial" (CBS, 1975). During his tenure on "L.A. Law", he made several other TV-movies, such as "Mistress" (CBS, 1987) and "She Says She's Innocent" (NBC, 1991). Rachins has also appeared in the episodic "Tales from the Crypt" (HBO, 1991), did hosting duty for "Macy's Thanksgiving Day Parade" (NBC, 1989), and was on the "14th Annual Circus of the Stars" (CBS, 1989). After "L.A. Law", he continued his eclectic TV appearances with several movies and guest spots. In June 1995, Rachins shot the busted comedy pilot "Nowhere East" (UPN). Returning to series TV, he was featured alongside Mimi Kennedy and Susan Sullivan as the older generation coping with the marriage of a free spirit and a conservative in the ABC sitcom "Dharma and Greg" (1997-)

Rachins returned to the big screen in "Thunder Run" (1986). Fortunately, because this rather dismal actioner had few bookings, and Rachins' role was small, it did no significant damage to his career. While continuing with his TV work, the actor also appeared in a handful of films, beginning with small, rather insignificant parts in the crime comedy "Heart Condition" (1990) and Rob Reiner's strange "North" (1994). He had his largest role in the erotic drama "Showgirls" (1995), which made most critics' worst films of the year list.