A fine outside shooter and a aggressive rebounding forward, Don Kojis starred for the Marquette basketball team and then was chosen in the second round in 1961 NBA draft by the Chicago Bulls and was immediately traded to the Baltimore Bullets. As a rookie, the 6 ft 3 inch, 202 pound Don Kojis scored 6.3 points per game. Then was traded to Detroit, 1964-65, 1965-66, then to the Bulls for one season.
After being traded to the San Diego Rockets prior to the opening of the 1967 season, Don Kojis played more minutes and averaged 19.7 ppg and 10.3 rebounds per game. He scored 1,360 points, connected on 530 of 1,189 field goals, for a .446 percentage and had 710 rebounds.
Playing adjacent with Basketball Hall of Fame of Fame forward Elvin Hayes, Don Kojis scored a career best 22.5 points per games in 1968-69, tenth highest in the NBA. The pair of forwards helped the Rockets make the NBA postseason playoffs, led by Elvin Hayes 28.4 ppg, the best among all NBA players. In six playoff games, 1968-69, Don Kojis averaged a very solid 20.2 ppg. He later played for Seattle and Omaha.