The on-loan Chelsea striker reached 12 goals for the season - all of which have come in the Barclays Premier League - firstly from the penalty spot and then when charging down a clearance from Sunderland goalkeeper Simon Mignolet.
The Black Cats set up a tense finish through Stephane Sessegnon's reply but Albion held on to keep up their challenge for a European place.
West Brom included Peter Odemwingie in their matchday 18 for the first time since his proposed move to QPR fell through amid acrimony last month and he was predictably booed by the home fans when his name was announced over the public tannoy before kick-off and when he made his late entrance onto the pitch.
The woodwork came to West Brom's rescue after 25 minutes when Steven Fletcher cut in from the left and saw his low shot beat the dive of Ben Foster and hit the far post.
West Brom responded and Youssouf Mulumbu headed wide from close range after attacking a probing Liam Ridgewell centre.
However, Lukaku put the Baggies ahead from the penalty spot for his 11th goal of the season after Craig Gardner was adjudged to have handled a cross from Ridgewell.
Sunderland started the second half on the offensive and Sessegnon had a shot cleared off the line by Mulumbu following a deep corner from Sebastian Larsson.
But Lukaku continued to trouble the Sunderland defence his perseverance forced Titus Bramble into a mis-timed back pass and he then charged down Mignolet's clearance which flew into the net.
Sunderland hit back and in the 80th minute Sessegnon curled a shot past Foster and over the head of Ridgewell on the line to reduce the arrears.
- Sports & Recreation
- Simon Mignolet
- West Brom