The deal includes a 2023 second-round pick to the Wizards, the source told ESPN.
The Athletic was first to report news of the trade.
The agreement comes one day after the Wizards announced star point guard John Wall, already out for the season with a left heel injury, will miss most — if not all — of next season as well because he needs surgery on his left Achilles tendon.
Washington entered Wednesday with a 22-31 record, 3.5 games behind the Miami Heat for the eighth and final playoff spot in the Eastern Conference.
The trade will provide significant financial savings for the Wizards, whose tax bill for this season will drop from $8.96 million to $3.34 million. The team will be $2.3 million below the tax threshold.
For 2019-20, Washington will have $89.5 million in guaranteed contracts, a savings of $28 million.
Parker has a $20 million team option that needs to be exercised by June 29. Portis is on an expiring contract, and the Wizards will have until the end of June to submit a $3.6 million qualifying offer.
ESPN’s Bobby Marks contributed to this report.