Bereaved individuals often experience sleep problems. The aim of this study was to evaluate feasibility and preliminary effects of internet-delivered cognitive behavioral therapy for insomnia (iCBT-i) in bereaved parents. Parents were randomized to iCBT-i (n = 10) or an active control group (n = 11). Primary outcome (insomnia) and secondary outcomes (prolonged grief, depression, posttraumatic stress, and grief rumination) were assessed pre- and post-treatment, with 9- and 18-month follow-ups. Feasibility was assessed post-treatment and one month later. Most parents reported positive effects of the treatment. The intervention group improved significantly from pre- to post-treatment and had a significantly larger reduction of insomnia when analyzed over all four time-points (Wald χ² = 30.0, p < 0.001), although the effect at post-treatment was very small (d = 0.1) for insomnia. Thus, iCBT-i was feasible and was related to reduced insomnia and psychological distress in bereaved parents, both short- and long-term, but the results regarding the treatment effect are preliminary due to the small sample size.