Across the U.S., obesity and overweight represent a rapidly growing public health concern that have been associated with expensive and debilitating outcomes such as depression, cancers, diabetes, and other metabolic disorders, cardiovascular disease, and significant disruption in quality of life, in addition to the tremendous public health costs. The current study examined a brief, randomized-controlled trial of acceptance and commitment therapy (ACT) with overweight and obese young adults. The results of this study hold important implications for future research in the utility of ACT to address overweight- and obesity-related lifestyle change. While the study was limited due to small sample size, it nevertheless suggested that weight-related psychological flexibility is an important construct to address and target in the treatment of overweight and obesity. It may be an effective means of decreasing emotional eating and improving a sense of control while eating. The findings support previous research supporting ACT as an empirically supported intervention for improving the quality of life of adults struggling with overweight and obesity. Results from this study are encouraging and support the utility of ACT, even in brief format, to possibly improve the lives of overweight and obese young adults. Study participants were randomly assigned to a 4-week experimental ACT group or an information control group, which received psychoeducational materials regarding lifestyle behaviors recommended by the Centers for Disease Control and Prevention (CDC). The results of the current study broadly showed that the experimental intervention was effective at improving weight-related psychological flexibility, which was also associated with reductions in emotionally avoidant eating and uncontrolled eating. In addition, the study showed relationships between improvements in psychological flexibility and eating process variables.