The Baggies registered a comprehensive 3-0 win against the Blues at The Hawthorns in the Premier League.
England Under-21 international striker Berahino opened the scoring with a brilliant 20-yard strike in the ninth minute.
Chelsea midfielder Cesc Fabregas was sent off for kicking the ball at Chris Brunt just before the half-hour mark.
West Brom took advantage of their numerical superiority and made it 2-0 in the opening minutes of the second half, when Berahino scored from the spot after he was brought down by John Terry.
Brunt rounded off the win with an angled shot from a quick corner on the hour mark.
Following the victory, Berahino and Lescott made the following posts on Twitter:
Great way to end our season at home last night. Thanking all the fans for their support throughout the season— Joleon Lescott (@JoleonLescott) May 19, 2015
West Brom are now 13th in the Premier League table with 44 points from 37 matches. The Baggies’ final game of the season is against Arsenal away from home at the Emirates Stadium in North London on Sunday.