Paul Brown, the head coach of the Browns, hired Ulinski in 1954 to work with the team's linemen. Ulinski changed to the Browns' linebackers coach in 1963 after Brown was fired and Blanton Collier replaced him. He later served as an administrative coaching aide and the Browns' film coordinator before retiring in 1984. The Browns won three National Football League championships during Ulinski's coaching career, in 1954, 1955 and 1964. He was inducted into Marshall's athletics hall of fame in 1986. Ulinski died in 2006 after a bout with Alzheimer's disease.
John Brickels, an assistant coach for the Cleveland Browns in the new All-America Football Conference (AAFC), noticed Ulinski when he was playing at Marshall. Brickels had been a high school coach in Huntington, West Virginia, where Marshall is located, and saw him in action again when he played for the Super-Bombers. At Brickels' urging, Ulinski signed with the Browns in 1946. The Browns finished that season with a 12–2 record and went on to win the first AAFC championship. Ulinski was named a second-team All-Pro. Cleveland won the AAFC championship again in 1947, when Ulinski began playing middle linebacker on defense in addition to his role on the offensive line.Paul Brown, the coach of the Browns, called him the best offensive guard in the AAFC, and said the team "discovered he is about as good a middle line backer as we have on the team".
Cleveland had a perfect season in 1948, winning all of its games, and Ulinski again was named a second-team All-Pro. The Browns repeated as the league's champions for a fourth year in a row in 1949, Ulinski's last season in professional football.
The following year, Brown hired Ulinski to replace Weeb Ewbank as the team's tackles coach after Ewbank resigned to become head coach of the Baltimore Colts. "We've looked forward to the day when Ulinski would return to our organization as a coach," Brown said after the signing, calling him a "fine student of football" and a player who could teach the game well. The Browns, who by the time Ulinski joined as a coach had moved to the National Football League (NFL), won championships in both of Ulinski's first two years as an assistant under Brown.
Paul Brown was fired 1963, two years after Art Modell took ownership of the team, but Ulinski stayed on the staff. Under his successor, former assistant Blanton Collier, worked primarily as a linebackers coach. The Browns won another championship while Ulinski was with the team in 1964.
Ulinski continued as the linebackers coach and worked as an administrative coaching aide until 1971, when he was named the team's film coordinator. He held that position until he retired in 1984, having spent more than 30 years with the Browns as a player and coach. During his time in Cleveland, Ulinski coached numerous offensive linemen and linebackers who were fixtures of the Browns' successful teams of the 1950s and 1960s, including Gatski, Lou Groza, Dick Schafrath, Abe Gibron, Mike McCormack and Gene Hickerson. Gatski, Groza, McCormack and Hickerson were all later inducted into the Pro Football Hall of Fame.