Wilson will count $2 million against the salary cap over the length of the deal. He will earn $1.75 million next season and $2.25 million in 2017-18.
Capitals general manager Brian MacLellan announced on Thursday they had agreed to the new deal with Wilson, a pending restricted free agent.
The 22-year-old had seven goals, 16 assists and 163 penalty minutes in 82 games last season for the Capitals, who drafted him 16th overall in 2012. In 231 NHL games, the Toronto native has 14 goals, 36 assists and 486 penalty minutes.