Nurses may experience frequent nightmares due to stressful work environments. Nightmares may also exacerbate stress among nurses, although this has yet to be tested empirically. We examined daily bidirectional associations between stress severity and nightmares, and moderation by post-traumatic stress disorder (PTSD) symptoms. 392 nurses (92% female; 78% White) completed 14 days of sleep diaries to assess previous-day stress severity and nightmare occurrence and severity. PTSD symptoms were assessed at baseline. Multilevel models were used to examine bidirectional, within-person associations between daily stress and nightmares, and cross-level moderation by baseline PTSD symptoms. 47.2% of nurses reported at least one nightmare across the two weeks. Days with greater stress were associated with higher odds of experiencing a nightmare (OR=1.22, p=0.001), as well as greater nightmare severity (b=0.09, p=0.033). Nightmare occurrence was associated with greater next-day stress severity (b = 0.15, p < 0.001). Daily stress and nightmare associations were similar for those with and without PTSD symptoms. Nightmares and stress may occur in a bidirectional fashion. Nurses face intense occupational demands and frequent exposure to potentially traumatic events. Studies should explore whether targeting nightmares and stress may improve nurses' health and well-being.