In a cross-sectional study, the prevalence rates of overall and specific mental health problems (MHP), as well as consequential impairments, were examined in a representative community sample of German preschoolers. MHP in 391 children were assessed by applying the Strength and Difficulties Questionnaire, as well as its impact supplement. Furthermore, the child behaviour checklist 1½–5 (CBCL 1½–5) and the IOWA-Conners behaviour rating scale were applied. Prevalence rates of MHP with 95 % confidence intervals (95 % CI) were determined. Odds ratios were calculated to analyse the relationships between MHP, age, gender, socioeconomic status, and geographical region using logistic regression. Overall, 7.4 % of the children showed symptoms of MHP. 12.9 % of the children were considered to be impaired by psychosocial problems. Depressive and anxiety symptoms were present in 4.2 % of the children; 11.8 % showed hyperactivity symptoms. The observed prevalence rates call for early mental health prevention in preschoolers.