The couple was attending the nuptials of one of Szohr's pals in Milwaukee when they decided to treat guests at the wedding reception to a racy dance.
The stars hit the dancefloor and began grinding their hips before Szohr convinced her boyfriend to give the bride a special treat.
Photographs published in America's Star magazine show Westwick dancing seductively for the newlywed and later unbuttoning his shirt to show off his toned pecs.
But his raunchy antics didn't sit well with the groom.
A source tells the tabloid, "It was crazy! The bride loved it, but halfway through the song the groom came up and stole her away! He was kind of jealous."
However, there was no need for the groom to worry - because Westwick and Szohr only had eyes for each other.
The insider adds, "You could tell they really love each other."