The young adult (YA) cancer community represents an understudied population in interpersonal and health communication scholarship. Through qualitative analysis, this study sought to advance a dark side perspective by exploring the content of messages shared in an online support forum for YAs with cancer. Our findings highlight a variety of complexities YAs face in an online cancer support community, including the light and dark of soliciting support, disclosing to a community, advocacy online, negative sentiment evaluating health care services, and asynchronous communication. Understanding the light and dark nuances involved with participating in an online YA support forum advances a dark side perspective on the scholarly research in health communication that can ultimately help care providers recommend resources and coach YAs to optimally and effectively use and navigate online support groups.