Garnett missed the last eight games due to left ankle inflammation, while Pierce sat out Friday's loss to the Cleveland Cavaliers due to a sore right ankle. The duo will join a new-look starting lineup alongside Avery Bradley, Jeff Green and Brandon Bass.
Bradley suffered a bruised collarbone in Friday's loss and sat out practice on Saturday, but is in the lineup despite lingering soreness.
Celtics coach Doc Rivers said Garnett and Pierce felt good after going through Saturday's practice session, and he doesn't expect any limitations for either.
"I'll watch Kevin. I doubt if he plays his normal 30 minutes, so I'll watch him, but there's no limitations by any of the doctors or anything," Rivers said.
Rivers also said it will be "nice" to have nearly a full roster available against the Wizards.
"It'll be nice to look down the bench and see more guys down there," he said. "That'll be nice. I wouldn't be surprised to be a little rusty because of [the time missed] ... [but] it's nice because you have time to try to get some kind of rhythm back."