The Worksop man traded birdies and bogeys almost in equal measure around the Hoylake course before battling par at the last saw him end with a one-under-par round of 71.
That leaves him five shots behind the lead set by his Ryder Cup team-mate Rory McIlroy, who carded a 66.
However, McIlroy was among the early starters on the day and the morning conditions proved better for scoring than those the afternoon starters like Westwood encountered.
Westwood went into his opening round looking to find some form and got himself to two-under par early on after back-to-back birdies at the fourth and fifth holes.
He gave a shot back at the seventh after he found a bunker and then missed a difficult par putt.
He bounced back straight away on the eighth by sinking a long birdie putt.
But he missed the green to the right of the par-three ninth and then missed the par putt to go back to one-under at the halfway point of his round.
However, he made a brilliant start to his back nine with a fabulous second shot into the par-five 10th.
He missed the eagle putt but made no mistake with securing the birdie.
But, once again, he quickly gave it back after finding thick rough on the 12th and failing to get up and down in the regulation four strokes.
The frenetic action around the turn seemingly left everyone breathless and Westwood’s round then calmed down with five pars in a row.
A wayward drive on the last then left him in a fairway bunker and in danger of dropping a shot.
But a great third shot to the back of the green from 250 yards and then a fine putt from 50 feet left him with a tap-in for par and still right in contention for that elusive first major.