<b><i>Background:</i></b> Sleepwalking (SW) is found to affect children predominantly, but it can persist or appear de novo even among adults. In this study, we assessed the demographic, clinical and polysomnographic profile, trigger factors and associated comorbidities of adult-onset (AO-SW) and childhood-onset (CO-SW) adult sleepwalkers. <b><i>Methods:</i></b> In adult sleepwalkers, a structured clinical interview, a battery of questionnaires, video-polysomnography (v-PSG) and standard electroencephalography (EEG) were performed. <b><i>Results:</i></b> Among 63 sleepwalkers, 45% had ≥1 episodes/month, 54% had partial recall of the episodes and 36% reported trigger factors for SW. Almost all subjects reported co-occurring parasomnias. In v-PSG, 4% exhibited episodes of SW, 17% confusional arousals, 21% had an increased apnea-hypopnea-index and 6% exhibited features of an overlap parasomnia disorder. In our cohort, 73% reported CO-SW and 27% AO-SW. In subjects with AO-SW, positive family history for parasomnias was found in 33% (vs. 49% in CO-SW), neurological comorbidities in 44% (vs. 14%), psychiatric comorbidities in 25% (vs. 33%), EEG abnormalities in 50% (vs. 29%). Violence during SW episodes was more frequent in males and in subjects with CO-SW (45% for self-injury and 44% for violent behaviour vs. 33 and 29% respectively in the AO-SW group). <b><i>Conclusions:</i></b> Adult SW represents a complex and potentially dangerous condition. The characteristics of AO-SW often differ from those of CO-SW.