The 6-foot-10 inch Bosh suffered a sprained right knee in the fourth period of Toronto's 115-107 loss to the Los Angeles Lakers Feb. 4.
"I'm extremely excited for myself, for the organization, and for my teammates," Williams told the Cleveland Plain-Dealer newspaper after hearing the news before Tuesday's 96-95 loss to the Indiana Pacers.
The Cavaliers were angry when Williams originally was not named to the Eastern squad Jan. 22 when all-star starters were announced, and not Jan. 29 when reserves were announced.
In this his sixth NBA season, the former Alabama product has per-game averages of 17.1 points, four assists, and more than three rebounds in 50 contests.
This will be his first all-star appearance.
Bosh said he plans to attend this weekend's festivities, and the game on Sunday in Phoenix.