Solange Knowles was caught on surveillance lashing out at the rapper, 44, in an elevator as they left the glamorous bash held in the Boom Boom Room at The Standard Hotel.
The 'XO' hitmaker appeared to be watching on helplessly as her sibling, 27, kicked and clawed her husband in what seemed to be an unprovoked attack.
In the footage, obtained by TMZ.com, Jay didn't appear to retaliate as the singer screamed in his face and, at one point, he even tried to hold her arms down as another man, who was presumably their bodyguard, held her back.
The bodyguard can even be seen pushing the emergency stop button repeatedly as the elevator reached the 12th floor in a bid to keep the violent altercation private.
Beyoncé - who has two-year-old daughter Blue Ivy with Jay - finally intervened and said something to Solange after she broke free and began punching him again.
Solange then stormed out of the elevator with a disgruntled expression plastered across her face as Beyoncé, 32, and Jay followed shortly behind.
The siblings were then seen getting into a car together, while the 'Holy Grail' hitmaker left on his own.