Fatigue, depression, and sleep disturbance are common adverse effects of cancer treatment and frequently co-occur. However, the possibility that inflammatory processes may underlie this constellation of symptoms has not been examined. Women (N = 103) who had recently finished primary treatment (ie, surgery, radiation, chemotherapy) for early-stage breast cancer completed self-report scales and provided blood samples for determination of plasma levels of inflammatory markers: soluble tumor necrosis factor (TNF) receptor II (sTNF-RII), interleukin-1 receptor antagonist, and C-reactive protein. Symptoms were elevated at the end of treatment; greater than 60% of participants reported clinically significant problems with fatigue and sleep, and 25% reported elevated depressive symptoms. Women treated with chemotherapy endorsed higher levels of all symptoms and also had higher plasma levels of sTNF-RII than women who did not receive chemotherapy (all P < .05). Fatigue was positively associated with sTNF-RII, particularly in the chemotherapy-treated group (P < .05). Depressive symptoms and sleep problems were correlated with fatigue but not with inflammatory markers. This study confirms high rates of behavioral symptoms in breast cancer survivors, particularly those treated with chemotherapy, and indicates a role for TNF-α signaling as a contributor to postchemotherapy fatigue. Results also suggest that fatigue, sleep disturbance, and depression may stem from distinct biologic processes in post-treatment survivors, with inflammatory signaling contributing relatively specifically to fatigue.