Wilson has played in seven games with the Capitals this season. His entry-level contract kicks in after he plays in his ninth game.
"It's huge. It's awesome. It definitely makes me feel a little more comfortable," Wilson said in meeting with reporters after he received the news from general manager George McPhee and coach Adam Oates.
The 19-year-old made his NHL debut during last season's Stanley Cup Playoffs, playing three games in the Capitals' first-round series loss to the New York Rangers.
Extremely excited to have this opportunity. Thanks to all of you for the constant support!— Tom Wilson (@tom_wilso) October 18, 2013
Prior to joining the Capitals, Wilson had 23 goals and 58 points in 48 games last season with the Plymouth Whalers of the Ontario Hockey League.
Wilson would have gone back to Plymouth if the Capitals had opted not to keep him. At 19, he's too young to play in the American Hockey League.
Instead, he'll remain in Washington and continue to work at improving his game.
"I think just keep doing the stuff I've been doing, working hard," he said. "They want to make sure I'm getting better every day. Come in, work hard. They don't want me to take this for granted. They don't want me to get too comfortable. They want me to keep developing and working as hard as I can to get better every day."
A first-round pick (No. 16) of the Capitals in the 2012 NHL Draft, he is scoreless with 14 penalty minutes and a minus-2 rating this season while playing a fourth-line role.
"I think the fourth line so far has done a fairly good job about generating as much offense as we can, but there's something to be said about finishing it when we do get those opportunities," Wilson said.