Antetokounmpo had missed the Bucks' previous two games because of a hyperextended left knee, which he suffered in Game 4 of the Eastern Conference Finals against the Atlanta Hawks.
League sources told ESPN that Antetokounmpo was undergoing around-the-clock treatment for the knee injury with hopes of being cleared to compete in the opening game of the championship series.
Ahead of Game 1, Antetokounmpo participated in his normal pre-game warmup routine while wearing a protective sleeve over the injured knee. Earlier Tuesday, the Bucks upgraded the two-time NBA MVP from doubtful to questionable.
Antetokounmpo has averaged 28.2 points, 12.7 rebounds and 5.2 assists over 37.4 minutes per game in the playoffs.
Game 1 of the Finals is set to tip off at 9 p.m. EDT Tuesday at Phoenix Suns Arena in Arizona.
The Suns beat the Los Angeles Clippers in six games to reach their first Finals since 1993. The Bucks edged the Hawks in six games for their first trip to the Finals since 1974.