Tomjanovich was selected in the 1970 NBA draft as the second overall pick by the San Diego Rockets (the franchise relocated to Houston in 1971), for whom he would play the entirety of his NBA career. He was also drafted in both 1970 and 1974 by the Utah Stars of the ABA. In his eleven years in the NBA, Tomjanovich had a scoring average of 17.4 points and a rebounding average of 8.1, earning five All-Star Game selections in the process (1974–1977, 1979). He is the fourth-leading scorer in Rockets history behind James Harden and Hall of Famers Calvin Murphy and Hakeem Olajuwon. Because his last name was so long, the back of Tomjanovich's jerseys would read "RUDY T.", rather than his 11 character name.