Posttraumatic stress disorder (PTSD) is characterized by sleep impairment and nightmares. As pleasant odors presented during sleep affect the emotional tone of dreams without inducing arousal, we investigated whether sleep patterns in PTSD can be improved via nocturnal olfactory stimulation. Participants were 40 inpatients with PTSD (n = 35 women; age range: 20-59 years) who completed a randomized, patient-blind, placebo-controlled trial. Baseline measurement for 5 consecutive nights was followed by a 5-night experimental intervention or placebo trial. During the intervention, patients received nocturnal stimulation with a pleasant odor (odor condition) or clean air (placebo condition) via an olfactometer that delivered inspiration-triggered stimuli in a nasal tube or via an odorized nasal clip. After each night, the patients completed standardized questionnaires that assessed sleep parameters and dream content. Each night, sleep efficiency, sleep onset latency, and wakefulness after sleep onset were monitored with a motion biosensor. Baseline assessment revealed that PTSD severity was associated with poorer sleep outcomes. An interaction effect showed that nocturnal odorization affected dream intensity. Post hoc tests revealed an improvement in the group that used the nasal clip as compared to baseline, d = 0.68. No negative effects were observed after odorization with the nasal clip. Considering the limited sample size, the study indicates that nocturnal olfactory stimulation may serve as a low-cost concomitant intervention to improve sleep quality in PTSD.