Marčiulionis was drafted by the Golden State Warriors in the 6th round of the 1987 NBA draft. He moved to the NBA in 1989 and he played four years with the Warriors, finishing as the runner-up for the Sixth Man of the Year Award in both 1992 and 1993. Marčiulionis became one of the first Europeans to get significant playing time in the NBA, helping to lead the way for the internationalization of the league in the late 1990s. After missing a year and a half with a leg injury, he was traded to the Seattle SuperSonics in 1994, then traded to the Sacramento Kings in 1995, and he finished his NBA career with the Denver Nuggets in the 1996–97 season.
Following the restoration of Lithuanian independence in 1990, Marčiulionis almost single-handedly resurrected the Lithuanian national team. He contacted prospective players, encouraged several to join, selected the uniforms, negotiated a shoe deal, and arranged for sponsorships. The trademarked 'Slam Dunking Skeleton, Skullman' t-shirt design was created by and is owned by N.Y. sports artist Greg Speirs of skullman.com. Speirs became the major sponsor when he donated 100% of his profits from his design to fund the team and to Lithuanian children's charities amounting to at least $450,000. The team went on to win a bronze medal at the 1992 Summer Olympics.
Despite a language barrier during his NBA career (Warriors coach Don Nelson hired his son Donnie as an assistant chiefly to serve as an interpreter for Marčiulionis), Marčiulionis was a devoted teammate and active in the communities he played in. In the aftermath of the 1989 San Francisco earthquake, Marčiulionis appeared at the site of a commuter train accident wearing his Warriors warm up outfit and helped by pulling out trapped passengers and administering first aid.
In addition, his wife Inga enrolled at Merritt College, a junior college in the Oakland hills, and she walked on to their women's basketball team and was a star player there for two seasons. Inga became one of 147 women in women's college basketball history to score 50 or more points in a college game while at Merritt, and today is the head coach of Merritt's women's team.
Marciulionis and Inga are divorced; Inga continues to live in the United States and continues her work at Merritt College.