The 24-year-old midfielder moves back stateside after a season and a half with TFC.
The 24-year-old Los Angeles native was acquired from Toronto FC in exchange for allocation money, the clubs announced on Tuesday.
“Luis Silva is a fine player and an outstanding young man and this was a tough decision," TFC president and general manager Kevin Payne said in a statement. "But we are bringing in new attacking talent this window and Luis' playing time would likely suffer.
“This move helps give us more flexibility now and for the future. We wish Luis nothing but the best.”
Silva was drafted fourth overall in the 2012 MLS SuperDraft, and he made 54 competitive appearances for Toronto. He scored seven times.
In D.C. United, Silva heads to a team struggling in all areas of the pitch, but especially in the offensive third. The Eastern Conference cellar-dweller has scored only eight goals in 19 MLS matches so far this year.
“Luis is an exciting and creative young player with tremendous technical ability,” D.C. general manager Dave Kasper said. “He has shown the capacity to manufacture and score goals.
"We’re excited to add a player of his caliber to a dynamic young core of players.”