Concussion underreporting contributes to the substantial public health burden of concussions from sport. Teammates may be able to play an important role in encouraging injury identification and help seeking. This study assessed whether there was an association between beliefs about the consequences of continued play with a concussion and intentions to engage as a proactive bystander in facilitating or encouraging teammate help seeking for a possible concussion. Participants were 328 (male and female) members of 19 U.S. collegiate contact or collision sports teams. Athletes who believed that there were negative health or performance consequences of continued play with a concussion were significantly more likely than their peers to intend to encourage teammate help seeking, but not more likely to alert a coach or medical personnel. Additionally, athletes who believed that their teammates were more supportive of concussion safety were more likely to intend to engage as proactive bystanders in encouraging teammate help seeking. Exploring how to encourage bystander promotion of concussion safety is an important direction for future programming and evaluation research and may provide an opportunity to improve the effectiveness of concussion education.