'Four years ago I was dating this guy named Robert,' she said. 'We broke up and then we got back together and for some reason it made Donald Trump go insane.'
The actress quoted several tweets by the president, in which he accused her of cheating on Pattinson 'like a dog' and urged the actor to break up with her. At one point, Trump even invited Pattinson to the Miss Universe pageant - prompting Stewart to say the mogul most have had a crush on the actor.
'I'm here to promote my movie Twilight, which this week has been on iTunes for eight years,' Stewart began.
'I'm a little nervous to be hosting because I know the president is probably watching and I don't think he likes me that much. Here's how I know.'
She then recounted Trump's string of tweets in which he said Pattinson could 'do better' than Stewart and urged him several times to break up with her.
'Robert Pattinson should not take back Kristen Stewart. She cheated on him like a dog & will do it again--just watch. He can do much better!' Trump tweeted in October 2012, four years before being elected president
The mogul even invited Pattinson to the Miss Universe pageant. He owned the franchise at the time.
'Miss Universe 2012 Pageant will be airing live on @nbc & @Telemundo december 19th. Open invite stands for Robert Pattinson,' Trump wrote.
'So to be fair,' Steward said Saturday, 'I don't think Donald Trump hated me. I think he's in love with my boyfriend.'