The objectives of this study were to assess within-person hypotheses regarding temporal cognition-pain associations: (1) do morning pain flares predict changes in two afternoon adaptive and maladaptive pain-related cognitions, and (2) do these changes in afternoon cognitions predict changes in end-of-day pain reports, which in turn, carry over to predict next morning pain in individuals with fibromyalgia. Two hundred twenty individuals with fibromyalgia completed electronic assessments of pain intensity, pain catastrophizing, and pain coping efficacy three times a day for three weeks. Multilevel structural equation modeling established that afternoon catastrophizing and coping efficacy were parallel mediators linking late morning with end-of-day pain reports (controlling for afternoon pain), in line with prediction. Catastrophizing was a stronger mediator than coping efficacy. Moreover, afternoon cognitions and end-of-day pain reports served as sequential mediators of the relation between same-day and next-day morning pain. These findings align with assertions of cognitive-behavioral theories of pain that pain flares predict changes in pain both adaptive and maladaptive cognitions, which in turn, predict further changes in pain.