This systematic review aimed to evaluate the effect of eHealth-delivered interventions for adults who undergo bariatric surgery on postoperative weight loss, weight loss maintenance, eating psychopathology, quality of life, depression screening, and self-efficacy. Six electronic databases were searched, with 14 studies (across 17 reports) included, involving 1633 participants. With substantial heterogeneity, qualitative descriptions have been provided. Interventions were delivered via an online program or internet modules (n = 2), telephone (n = 2), text messages (n = 2), videoconferencing (n = 3), mobile application (n = 1), and audiovisual media (n = 1). Three studies included a combination, including internet modules and telephone (n = 1), wireless fidelity scales, emails, and telephone (n = 1), and a combination of online treatment, weekly emails, and access to a private Facebook group (n = 1). All the eHealth interventions, except for one, implemented behavior change techniques, including self-monitoring, problem solving, social support, goal setting, and shaping knowledge. Both eHealth intervention and control groups lost weight across the included studies, and eHealth was found to be as effective as or more effective than the control for weight loss. Two studies measured weight loss maintenance; both eHealth and control groups regained weight in the longer term. The interventions showed significant improvement on assessment measures for eating psychopathology. In conclusion, when bariatric surgery patients have limited or no access to healthcare teams or require additional support, eHealth may be a suitable option. Future studies implementing eHealth interventions would benefit from reporting intervention components as per the behavior change techniques taxonomy and further consideration of delivering eHealth in a stepped care approach would be beneficial.