BOSTON—Canadian Kelly Olynyk scored a career-playoff high 26 points and the Boston Celtics used a big fourth quarter to outlast the Washington Wizards 115-105 in Game 7 of the Eastern Conference semifinals Monday night.

Boston advances to the Eastern Conference final, where it will host the Cleveland Cavaliers in Game 1 on Wednesday.

“What a special opportunity to get a chance to compete against them,” Boston coach Brad Stevens said.

Isaiah Thomas led Celtics scorers with 29 points, plus 12 assists, but the Celtics got a huge lift from Olynyk and the rest of their bench, outscoring their Wizards’ counterparts 48-5. Boston also connected on 11 three-pointers, including 8 of 13 in the second half.

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“Everyone gave their best tonight, and it turned out well,” said Olynyk, who grew up in Kamloops, B.C. “It was a team effort, hard work. It was a tough seven-game series. Both teams played hard. We outlasted them there. They are a great team. They made big shots all series.”

Bradley Beal led the Wizards, playing their first Game 7 since 1979, with 38 points — including 24 in the second half. Otto Porter added 20 points. John Wall and Markieff Morris each finished with 18. But Washington also commited 15 turnovers leading to 17 Celtics points.

Boston trailed 76-72 late in the third quarter before a 13-3 spurt. The run grew to 22-5 in the opening minutes of the fourth as the Celtics’ lead became 94-81.

But Washington quickly responded, scoring seven straight in just 51 seconds to get back within six.

Washington stayed close as Beal continued to score, including a four-point play. Then Olynyk took over. He scored 11 of 13 points for Boston as the Celtics stretched their advantage to 110-100.

“I knew it would come down to the last six minutes of the game,” Washington coach Scott Brooks said. “They had that little run at the start of the fourth quarter.”

Marcus Smart, Amir Johnson and Olynyk all were whistled for three fouls in the opening 24 minutes, though Smart did inject some life into a second unit that outscored their Wizards’ counterparts 19-5.