Introduction. There are different interventions for the fear of cancer recurrence. However, studies showing which is the most effective in digital modality are still lacking. Purpose. To evaluate the effects of Internet delivered cognitive behavioral therapy (ICBT) and Relaxation Training (RT) administered online in cancer survivors. Method. A pretest-posttest design with control group was used. Inclusion criteria were primary treatment for completed cancer and score ≥ 16 on the severity subscale of the fear of cancer recurrence inventory. The ICBT involved 8 sessions that included psychoeducation, cognitive restructuring, coping strategies, acceptance and commitment, and relaxation techniques. The RT group received three relaxation techniques such as diaphragmatic breathing, deep diaphragmatic breathing with counting, and the body scanning technique. Both groups completed the Fear of Cancer Recurrence Inventory before and after the intervention. The Wilcoxon test was performed for group comparisons. Results. Participants in the ICBT group (n=6) only obtained significant differences in the severity subscale (Pre M= 20.6, Post M= 12.3; Z=-2.20, p=.027; η²= 14.3). The subscale of triggers (Pre M= 17.5, Post M= 10.5; Z=-1.78, p=.075; η²= 14.0), and coping strategies (Pre M= 24.5, Post M= 31.0; Z=-1.80, p=.072; η²= 14.0), were at the limit of significance with large effect size. In the RT group (n=11) significant differences were obtained in the subscales of severity (Pre M= 22.0, Post M= 14.0; Z=-2.60, p=.009; η²= 13. 0), psychological distress (Pre M= 11.0, Post M= 5.0; Z=-2. 05, p=.040; η²= 12.9), functioning impairments (Pre M= 10.0, Post M= 2.0; Z=-2.82, p=.005; η²= 13.0) and insight (Pre M= 7.0, Post M=2.0; Z=-2.81, p=.005; η²= 13.0) all with medium effect size. Conclusions: Internet delivered cognitive behavioral therapy and Relaxation Training can decrease clinical levels of fear of cancer recurrence, larger effect sizes are observed for ICBT.