Among persons with posttraumatic stress disorder (PTSD), the severity of symptoms and concurrent distress are not fully explained by trauma severity. Interest has consequently arisen in the psychological processes that cause distress and heighten PTSD symptoms. This study accordingly sought to examine whether differences in metacognitive capacity are related to levels of emotional distress, avoidance/numbing, and hyperarousal. Participants were 48 adults with a confirmed diagnosis of PTSD. Comparison groups included 51 adults with HIV and 183 with schizophrenia. Metacognition, emotion recognition, depression, and emotional distress and levels of avoidance/numbing and hyperarousal were assessed concurrently using the Metacognition Assessment Scale-Abbreviated, the Bell Lysaker Emotion Recognition Test, the Beck Depression Inventory, and the Clinician-Administered PTSD Scale. Results revealed that the PTSD group had better ratings of overall metacognitive capacity than the schizophrenia group and specifically poorer levels of metacognitive mastery, or the ability to use metacognitive knowledge to respond to challenges, than the HIV group. Within the PTSD group, poorer metacognitive mastery was linked with greater distress and higher hyperarousal when depression was controlled for statistically. Emotion recognition was not linked with distress or symptom severity. Results are consistent with models in which symptom severity in PTSD is related to the extent to which persons can use knowledge of themselves and others to find ways to respond to distress that match their own unique needs.