The Cavs, who currently sport the best record in the NBA at 43-11, sent their top 2010 draft pick and the rights to forward Emir Preldzic to Washington in a deal that also saw them acquire point guard Sebastian Telfair from the Los Angeles Clippers.
The Clippers got Drew Gooden from the Wizards and sent forward Al Thornton, the Clippers' first-round draft pick in 2008, to Washington.
All six players involved in the transaction must either pass physicals or have their physicals waived by their new team, The (Cleveland) Plain Dealer reported Wednesday.
Jamison is a former all-star who played for Team USA and is averaging 20.5 points and 8.8 rebounds per game for Washington this season.
Ilgauskas is the all-time Cavs leader in rebounds, blocked shots and games played.
The NBA trade deadline is 3 p.m. Thursday.