The current study extended research linking trait perfectionism with health symptoms by examining perfectionism from a cognitive perspective focused on perfectionistic automatic thoughts in psychosomatic symptoms. It was postulated that a cognitive preoccupation with needing to be perfect is a specific form of rumination implicated in health problems. In addition, we evaluated daily hassles and negative affect as possible mediators of the link between perfectionistic automatic thoughts and psychosomatic symptoms. A sample of 228 participants completed the Perfectionism Cognitions Inventory and measures of daily hassles, positive affect, negative affect, and psychosomatic symptoms. As expected, perfectionistic automatic thoughts were linked significantly with psychosomatic symptoms, daily hassles, and trait negative affect. Tests of mediational effects indicated that daily hassles and negative affect mediated the link between perfectionistic automatic thoughts and psychosomatic symptoms and this pattern held for both men and women. The results indicate that people with frequent thoughts about needing to be perfect are susceptible to experiencing more frequent psychosomatic symptoms and should benefit from stress reduction training and cognitive-behavioral interventions focused on reducing these thoughts.