Bartoli collected her second championship of 2011 -- she won at Eastbroune in June -- and seventh overall with a 6-3, 6-1 win over the top-seeded Stosur.
Rain washed out Friday's quarterfinals, pushing those four matches back one day and putting the semifinals and finals both on Sunday's schedule.
Stosur reached the finals with a 7-6 (7-5), 3-6, 6-3 win over Zheng Jie in a match that took more than 2 1/2 hours. Bartoli, the No. 2 seed, played for nearly an hour less in a 6-1, 7-6 (7-5) semifinal win over third-seeded Angelique Kerber.
That could have be a factor in the finals where Bartoli didn't drop serve and ended up winning 61 percent of the points in the match. She took more than two-thirds of the points and lost only four points in four service games in the second set.
Bartoli collected $37,000 for the victory while Stosur took home $19,000. Kerber and Zheng each earned $10,200 as semifinalists.
Swim Week Miami Beach 2014 [PHOTOS]