The standout defenceman's extension was next in line after the team signed both goaltenders Logan Thompson and Charlie Lindgren to new deals earlier this season.
Chychrun needs just one more goal to reach 19 on the season, which would be a new career high.
The 26-year-old already has a career high 43 points this season and currently ranks first among all defenceman with a +24 +/-.
Chychrun was originally acquired by the Capitals in a trade with the Ottawa Senators back in July 2024.
"I think this has just been such a great experience and it was something that if there was a number we were comfortable with, we were more than happy to stay and not test free agency," said Chychrun. "So, I’m really happy with things went and getting something done as we get towards the end of the season here and not have to think about it going into the playoffs. Just be able to go out and do everything we can to win."