The two sides were working out the parameters of the exchange, which could include cash or future considerations, sources said. But Cleveland will not be trading a player back to the Clippers.
The Clippers are making the move to clear a roster spot. The trade is not expected to be finalized until Monday or Tuesday.
Dekker, a three-year NBA veteran, played his first two seasons with the Houston Rockets, who drafted him with the 18th pick in 2015 out of Wisconsin.
He was acquired by the Clippers last June in the Chris Paul trade.
Dekker averaged 4.2 points and 2.4 rebounds in 12.1 minutes per game last season.
The trade of Dekker allows the Clippers to shed a much-needed roster spot before the start of training camp in late September. Not including point guard Patrick Beverley, who is on a non-guaranteed contract, Los Angeles has 15 guaranteed spots and will need to waive or trade another player before the start of the season if Beverley is to be retained.
For Cleveland, the trade provides depth to the forward position with restricted free agent Rodney Hood still unsigned.
The Cavaliers will acquire the $2.8 million expiring contract of Dekker with the $5.8 million trade exception created from the Kyrie Irving trade to Boston last August. The Clippers will now have a $2.8 million exception.
Information from ESPN's Bobby Marks was used in this report.