Dadonov, a 32-year-old forward, scored 20 points (13 goals, seven assists) in 55 games with the Senators last season. He has two seasons remaining on a three-year, $15 million contract ($5 million average annual value) he signed with Ottawa on Oct. 15, 2020.
"He really fit the bill for us," Golden Knights general manager Kelly McCrimmon said. "He was a player that we had a lot of regard for. There were some good forwards available in free agency that we liked that we would've turned to had we not completed the trade with Ottawa. Our priority was this player, and we were happy to add him. I think he's going to fit in very well.
"I think this is the best top-nine forwards our organization has had, and I think this is the best group of forwards collectively our team has had. A real positive addition to our team this morning."
Selected by the Florida Panthers in the third round (No. 71) of the 2007 NHL Draft, Dadonov has scored 222 points (104 goals, 118 assists) in 335 regular-season games with the Senators and Panthers and has one assist in four Stanley Cup Playoff games.
"I'm very excited," Dadonov said. "They're one of the best teams in the NHL right now. Every year they have a competitive team. I can't wait for the season to start.
"I wasn't expecting it. Ottawa's general manager called me and said, 'so we traded you.' He told me it was Vegas. It's part of my job."
Holden had two assists in 17 regular-season games with Vegas last season and seven points (two goals, five assists) in 15 playoff games. The 34-year-old defenseman has one season remaining on a two-year, $3.4 million contract ($1.7 million AAV) he signed with Vegas on Feb. 24, 2020.
Signed by the Columbus Blue Jackets as a free agent on March 28, 2008, Holden has scored 143 points (45 goals, 98 assists) in 513 regular-season games with the Golden Knights, Boston Bruins, New York Rangers, Colorado Avalanche and Blue Jackets. He has scored 17 points (seven goals, 10 assists) in 55 playoff games.
NHL.com independent correspondent Danny Webster contributed to this report
