The stars were first linked in February when they were spotted arriving together at friend's birthday part in Los Angeles.
An informant has now told Us Magazine that Efron and Collins recently reached a decision to part ways.
"They're no longer together... it was just a casual thing and it fizzled…They were never in the same place at the same time," the source said of Efron and Collins's busy schedules.
Another insider added that Efron "was never very serious about" Collins in their three months together.
The romance was Efron's first high-profile relationship since splitting from long-time love Vanessa Hudgens in 2010.
Efron next stars with Nicole Kidman in The Paperboy, opening later this year.
Watch a clip from The Paperboy below: