Purpose: While online interventions are increasingly explored as an alternative to therapist-based interventions for cancer-related distress, limitations to efficacy potentially include low uptake and adherence. Few predictors of uptake or adherence to online interventions have been consistently identified, particularly in individuals with cancer. This study examined rates and predictors of uptake and adherence to Finding My Way, a RCT of an online intervention versus an information-only online control for cancer-related distress. Methods: Participants were adults with cancer treated with curative intent. Adherence was assessed by login frequency, duration and activity level; analyses examined demographic, medical and psychological predictors of uptake and adherence. Results: The study enrolled 191 adults (aged 26–94 years) undergoing active treatment for cancer of any type. Uptake was highest for females and for individuals with ovarian (80%) and breast cancer (49.8%), and lowest for those with melanoma (26.5%). Adherence was predicted by older age and control-group allocation. Baseline distress levels did not predict adherence. High adherers to the full intervention had better emotion regulation and quality of life than low adherers. Conclusions: Uptake of online intervention varies according to age, gender and cancer type. While uptake was higher amongst younger individuals, once enrolled, older individuals were more likely to adhere to online interventions for cancer-related distress.