This study investigated predictors of adherence and outcome in a sample of callers to a national crisis telephone counseling service who were randomized to receive a 6-week, online, self-administered psychoeducation and cognitive behavioral therapy (CBT) intervention. Age, sex, relationship status, employment status, level of education, baseline depression symptom severity, and motivation to undertake the intervention were examined as predictors of adherence to the intervention in participants assigned to receive the online intervention (n = 83). Predictors of depression outcome were assessed using mixed models repeated measures ANOVA, comparing the two web-CBT intervention groups to the tracking and control groups (n = 155). Lower baseline depression severity was significantly associated with greater adherence to the intervention. A significant interaction was found between measurement occasion and motivation to undertake the intervention. At 6 month follow-up, participants with low and moderate levels of motivation had lower depressive symptoms than those with high levels of motivation. At 12 month follow-up, those with moderate levels of motivation had lower depressive symptoms than those with high motivation. The findings suggest that lower pre-intervention depression symptoms may positively influence adherence to online treatment for depression, while low and moderate levels of motivation appear to be optimal for treatment outcome. The factors that relate to adherence and outcome need to be understood to prevent dropout and maximize treatment effectiveness in online interventions.