Night eaters with severe obesity are more likely to be low in mood and unemployed compared with non-night eaters. Night eaters with severe obesity describe compulsive and uncontrolled eating. Research interest in night-eating syndrome (NES) has grown in recent years in line with increased rates of obesity. This study used a mixed-methods approach to investigate its characteristics in severe obesity. Eighty-one individuals (mean [standard deviation] age 44.6 [11.6] years, [body mass index] 50.0 [10.7] kg m(-2) ; 43% men) from a hospital-based UK obesity clinic were interviewed for NES based on 2003 criteria. Full and partial NES were combined into one night-eating behaviour (NEB) group (n = 31). Demographic and clinical characteristics were compared with those of non-NEB individuals (n = 50). NEB characteristics were also identified through exploratory thematic analysis of interview data. NEB individuals had lower mood (P = 0.01) and were less likely to be employed (P = 0.03). Differences in mean age and reported sleep duration were not significant. Thematic analysis of patient perceptions of NEB highlighted the potential heterogeneity of NEB development: NEB developed in childhood, adolescence and adulthood. Individuals reported long-standing and current sleep difficulties, negative affect and conflictful relationships. Night eating was solitary, compulsive and uncontrolled, and daytime eating patterns were chaotic. Accounts of awareness of night eating were conflicting. Severely obese night eaters are characterized by low mood and lack of employment. Further studies are required to explore behavioural and cognitive influences on night eating in severe obesity.