Richardson's fifth 3-pointer gave him 17 points and handed a decisive lead to the Magic, who finished the contest on an 11-0 run and claimed the first contest of their Eastern Conference quarterfinal series against the third-seeded Pacers.
The all-star center underwent season-ending back surgery last week and is out for the playoffs.
David West scored 19 points and grabbed nine rebounds for the Pacers, who didn't score in the final 4 minutes and missed nine straight shots down the stretch.
Danny Granger added 17 points and eight boards, but was whistled for traveling in the game's waning seconds.
Gal Gadot cast as Wonder Woman for 'Batman vs. Superman'
Jordana Brewster on Paul Walker: 'He was an enormous presence in my life'