This study aimed to evaluate the efficacy and patient acceptance of the first German-language Internet-based treatment for infertile patients. Infertile patients (N = 124) were randomly assigned to either an 8-week Internet-based cognitive-behavioral treatment, or to a waiting-list control group. Participants were assessed at treatment start, post-treatment, and at a 5-month follow-up. Outcome measures included mental health and pregnancy rate. From pre- to posttest, treated participants in contrast to controls did not show significant improvement, although between-group effect sizes were in favor of the intervention group on all mental health measures (Cohen's d ranged from 0.16 to 0.38). The intervention significantly reduced the depression level of clinically distressed and depressed participants. No effects were found regarding pregnancy rate. The treatment was assessed as positive or very positive by 80% of the participants; this finding coupled with the high demand for such support confirm that Internet-based interventions are a promising new approach for infertile patients that needs more development and testing.