The trade is pending physicals, the agent Tony Dutt said.
The move ends four up-and-down seasons for the mercurial Davis, who won a NBA title with the team his rookie season and blossomed into a key frontcourt contributor.
But his roller coaster confidence and frequent verbal sparring with coach Doc Rivers might have left the Celtics hesitant to commit to him long term. Instead, the team will use their rights to ink Davis to a contract extension before flipping him to Orlando.
In the 6-foot-8, 240-pound Bass, the Celtics get back a very similar player, one coming off his best season as a pro. Bass, a former second-round pick of the Hornets (33rd overall in 2005) started 51 games for Orlando last season, averaging 11.2 points and 5.6 rebounds over 26.1 minutes per game.
Davis averaged career highs at 11.7 points and 5.4 rebounds over 29.5 minutes per game. His shot selection was often questioned (he took 10.3 shots per game off the bench, most of which came from the perimeter).
Davis, a former second-round pick (35th overall in 2007) turns 26 on Jan. 1, while Bass turns 27 in late April. The two players are friendly having grown up together in Baton Rouge and both played collegiately at LSU.
Bass inked a four-year, $16 million contract with Orlando in July of 2009. He is scheduled to make $4 million this season with a player option at the same amount next year.
Chris Forsberg covers the Celtics for ESPNBoston.com.