McDowell, who was risen to 55th in the world rankings, finished with a one-under-par 69 to finish five strokes behind winner Adam Scott.
The Portrush player had started the day at three under, after an impressive 67 on Saturday.
It qualifies the 36-year-old for the WGC-Cadillac Championship which starts at Trump Doral on Thursday.
McDowell started his round with a birdie three on the first, and then bogeyed the fifth and birdied the eighth to reach the turn in one-under 34.
A dropped shot on 12 was recovered with birdie on the 13th to move into a top-five position.
Defending champion Padraig Harrington finished 43rd in the West Palm Beach tournament after a closing 71 put him on four-over-par 284.
Northern Ireland's Graeme McDowell has been buoyed by finishing fifth at the Honda Classic in Florida.