Posttraumatic stress disorder (PTSD) often develops following trauma. Nightmares may contribute to the development of PTSD. According to the neurocognitive model, cognitive and neural factors together form an emotion network and produce dreaming. Normal dreaming plays a role in fear extinction. However, when disruptions occur in this neurocognitive network, disordered dreaming such as nightmares occur. Among vulnerable individuals who are fear conditioned or primed for select emotional reactivity (i.e., a traumatic event), nightmares can activate previously encoded structures containing specific fear memories. This can lead to elevated waking distress and more intense/frequent nightmares. Based on this model, nightmares containing content related to the trauma should play a role in fear conditioning and reduce the chance for fear extinction. Although an association between nightmares and PTSD has been established, several sleep disturbances often co-occur among individuals displaying PTSD symptomology, and few studies are statistically powered enough to examine a number of PTSD-related sleep disturbances simultaneously to examine each disturbance’s unique contribution to PTSD. The current study examined the relationship between seven PTSD-related sleep disturbances and PTSD symptoms, in a sample of 983 college students. Further, we hypothesized that trauma-related nightmares would be associated with greater PTSD symptom severity after controlling for other PTSD-related sleep disturbances, including non-trauma-related nightmares. Results indicated that PTSD-related sleep disturbances predicted PTSD symptom severity. Moreover, trauma-related nightmares were most strongly associated with PTSD symptom severity. Moreover, nightmares and bad dreams not related to a specific traumatic event were not related to PTSD symptoms.