The young Hollywood couple, who were not serious about their relationship, have decided to call it quits, reported Daily Telegraph.
"They're no longer together. They were never serious though. It was just a casual thing and it fizzled. They were never in the same place at the same time.
"Zac was never very serious about her. He didn't talk about her to friends," a source said.
Efron, 24 and Collins, 23, were first seen holding hands at a friend's birthday party in Los Angeles back in February and were only photographed together once.
Efron was previously in relationship with his "High School Musical" co-star Vanessa Hudgens for five years and was also linked to Taylor Swift.