The objective of this study was to conduct an analysis of left-handed children treated in an urban mental health clinic to investigate the frequency and severity of psychiatric disorders compared to right-handed peers. Data on handedness, diagnoses, hospitalizations and severity of mental disorders were collected on 692 consecutive children, 4-18 years old (M=10.1, SD=3.2), referred for psychiatric evaluation. Left-handed children were 18.2% of patients in the study, a rate significantly higher than left-hand dominance in the USA (p<.05). Compared to children with right-handedness, logistic regression analysis yielded 31% [odds ratio (OR)=1.31, 95% confidence interval (CI): 1.15-1.50] higher odds of having more psychiatric diagnosis, 70% (OR=1.70, 95% CI: 1.10-2.62) increased odds of anxiety, 53% (OR=1.53, 95% CI: 1.03-2.27) increased odds of depression and 78% (OR=1.78, 95% CI: 1.21-2.62) increased odds of oppositional defiant disorder for children who were left-handed. Left-handed children had increased odds of being prescribed antipsychotic and anxiolytic medication uses, 53% and 86% increased odds, respectively, and 66% (OR=1.66, 95% CI: 1.08-2.55) increased odds of psychiatric hospitalizations. Left-handedness was a phenotypic risk factor for psychiatric disorders and increased severity of psychiatric disorders.