The Briton only just qualified for the season's first major by virtue of a top-50 ranking but his two-under total at Augusta was good enough to tie for second alongside Jordan Spieth, three shots behind compatriot Danny Willet.
It was a welcome return to form for Westwood, who is still searching for a first win since recording a third Indonesian Masters triumph in April 2015, with his poor results leaving him as low as 67th in the world rankings earlier this year.
"When you haven't played well for a long time, then you do start to have doubts in your mind," Westwood told British media.
"Playing well at the Masters was a kick I really needed. Obviously any time you play well in a tournament, especially the stature of the Masters, it gives you a lot of confidence and belief."
The 43-year-old finished 10th at last week's Irish Open on his return from a five-week break, boosting his chances of qualifying for a 10th straight Ryder Cup appearance at Hazeltine in September.
"It was nice to give (Europe captain) Darren Clarke a nudge that I could still play golf under pressure against the best players in the world," added Westwood, currently 35th in the world rankings.
"When you look at the records, there's not that many people played that many Ryder Cups. It would be nice to play a 10th one and get some more points for the team."