This study examined the effectiveness and feasibility of therapist-guided Internet-delivered exposure (EX) and behavioral activation (BA) for complicated grief and rumination. Forty-seven bereaved individuals with elevated levels of complicated grief and grief rumination were randomly assigned to three conditions: EX (N = 18), BA (N = 17), or a waiting-list (N = 12). Treatment groups received 6 homework assignments over 6 to 8 weeks. Intention-to-treat analyses showed that EX reduced complicated grief, posttraumatic stress, depression, grief rumination, and brooding levels relative to the control group at posttreatment (d = 0.7–1.2). BA lowered complicated grief, posttraumatic stress, and grief rumination levels at posttreatment (d = 0.8–0.9). At 3-month follow-up, effects of EX were maintained on complicated grief and grief rumination (d = 0.6–1.2), and for BA on complicated grief, posttraumatic stress, and grief rumination (d = 0.8–0.9). EX reduced depression more strongly than BA (d = 0.6). Completers analyses corroborated results for EX, and partially those for BA, but no group differences were detected. BA suffered from high dropout (59%), relative to EX (33%) and the waiting-list (17%). Feasibility appeared higher for EX than BA. Results supported potential applicability of online exposure but not behavioral activation to decrease complicated grief and rumination.