Kelly, 30, was in uniform for the Sens' 4-3 shootout loss to the New York Islanders at Scotiabank Place on Tuesday. The 6-foot, 198-pound center has 12 goals, 11 assists and 27 penalty minutes this season. He was drafted by the Senators in the third round (No. 94) of the 1999 Entry Draft.
"It's pretty tough to get traded … it's my first time," Kelly said. "But these things happen, especially the way things have gone this year. I'm excited to get an opportunity to play in the postseason and an opportunity to go late hopefully into the playoffs."
Ottawa (18-30-9) has the second-fewest points in the NHL with 45. The Sens are also 1-7-2 in their last 10 games and have won just two of their last 20. The Bruins are first in the Northeast Division; they and the Montreal Canadiens have 69 points, but the B's have a game in hand.
Boston also played Tuesday night, suffering a 4-3 loss to the Toronto Maple Leafs at TD Garden. Kelly will likely make his Bruins' debut when they return to action on Thursday against the Islanders at Nassau Veterans Memorial Coliseum.
Bruins GM Peter Chiarelli, who knew Kelly from his days in Ottawa before coming to Boston, was elated to get him.
"I've obviously had a connection with him in my time with Ottawa," said Chiarelli, who was the Sens' assistant GM for seven seasons. "He's a very good person and has good leadership character. He's under contract for next year. We're happy to have him in the organization."
Kelly's most productive season came in 2006-07, when he tallied 15 goals and 23 assists. He also had 7 points (3 goals, 4 assists) in 20 playoff games that postseason for the Sens, who lost to the Anaheim Ducks in the Stanley Cup Final.
"He has a lot of playoff experience," Chiarelli said. "He's a high-character person. He plays both ways. We needed a centerman that's going to give us some depth, and Chris can give us that and he can play up and down the lineup."
Kelly will only spend a couple of days out of town before returning to Canada's capital on Friday night when the Bruins will face Kelly's now-former team at Scotiabank Place.
"It'll be a weird feeling coming out on the other side of the rink," Kelly admitted. "Obviously, Ottawa's all I've known. I was drafted here and played my whole NHL career here. It'll be a bit different."