The continuity of mental disorders in street-working children is rarely studied. This study therefore investigated homotypic continuity, recurrence of the same disorder, and heterotypic continuity, when a new disorder follows on the previous, of mental disorders from childhood to adulthood in street-working boys from Duhok City, Kurdistan Region of Iraq. Mental disorders were assessed by structured diagnostic interviews in 40 street-working boys in 2004–2005 and again in 2021, when the participants’ mean ages were 12.1 (SD 1.8) and 29.7 (SD 2.3), respectively. Mental disorders were common; 24 participants (60%) satisfied the criteria for at least one diagnosis at baseline and 28 (70%) at follow-up. Comorbidity increased from 1.2 (SD 1.4) disorders initially to 2.5 (SD 1.8) at follow-up. Only anxiety disorders showed homotypic continuity. Depressive disorders exhibited the greatest increase over time whereas externalizing disorders exhibited a decreasing tendency. The number of mental disorders in adulthood was related to the number of mental disorders in childhood but not to the number of childhood traumas experienced, having previously worked for more than two hours per day, having worked for over two years on the streets, or having at least one dead parent as a child. Parental ratings on the Child Behaviour Check List (CBCL) from childhood were also unrelated to the number of adult disorders. More longitudinal studies with bigger samples of both genders are needed to fully evaluate the continuity of mental disorders in street-working children and to determine whether the number of mental disorders in childhood is a stronger predictor of being mentally disordered in adult life than psychosocial risk factors or experiences of internalizing or externalizing symptoms in childhood.