Monica took the stage to perform 'I Love The Lord', while Brandy followed with a performance of 'I'm Your Baby Tonight' and 'I Wanna Dance With Somebody'.
Monica later tweeted that she was "honoured" to be a part of the tribute, adding: "I'm still overwhelmed."
Meanwhile, Brandy said: "One of the best nights of my ENTIRE LIFE!!! Whitney Houston, I LIVE, and LOVE YOU 4ever!!!"
Houston's brother Gary followed them on to the stage, saying that he misses his sister "so much" and adding: "I love you back to life every day."
He sang 'Where You Are' before welcoming his mother Cissy to the stage, where she performed an emotional rendition of 'Bridge Over Troubled Water' to a standing ovation from the audience. She dedicated the song to "Nip", Houston's nickname, and a number of stars in the crowd appeared tearful.
Chaka Khan brought the tribute to a close with a performance of 'I'm Every Woman'.
Throughout the memorial, images of Houston appeared on a big screen behind the stage.
Watch the tribute to Whitney Houston at the BET Awards below:
> BET Awards 2012: The winners in full