Gomez, who recently split from singer The Weeknd, looked cheerful.
"Selena and Justin took a bike ride from her house... Justin was very sweet and held up Selena's bike for her as she got on. They were having a blast together.
"Justin was singing loudly and dancing with his arms in the air while riding down a busy street. Selena was laughing so hard she had to cover her mouth and try not to fall of her bike. She clearly thinks he is hilarious," a source told E! online.
Gomez and Bieber have been spending a lot of time together. Over the weekend, the duo was clicked having breakfast and attending church together.