A ball catcher for recovering balls from wellbore fluids containing sand during flow back operations. The ball catcher has a receiving chamber for receiving the wellbore fluids containing sand, a first flow outlet for discharging a portion of the wellbore fluids and sand contained therein, and a diverter for redirecting balls entrained within the wellbore fluids. The redirected balls and a balance of the wellbore fluids also containing sand are received in a ball-retaining chamber. A blocker fit to the ball-retaining chamber retains the recovered balls therein while the balance of the wellbore fluids and sand contained therein is discharged from a second flow outlet and directed to downstream equipment through an auxiliary flow line. The retaining chamber can be isolated allowing the balls to be removed from the ball catcher without disrupting the flow back operation.