The purpose of the present cross-sectional study was to assess the extent of agreement between clinical and self-assessed gingival health and to investigate possible factors associated with the amount of self-assessed gingival bleeding. A study group comprising students enrolled in grade 7 or 8 in Helsinki, Finland (n = 172), performed a self-assessment based on two tests: the amount of bleeding after toothbrushing and after interproximal tooth cleaning with toothpicks. Clinical examinations based on bleeding on probing (BOP%) were carried out by four local community dentists. The highest observed kappa value was 0.43 for the agreement between BOP% and self-assessment when tested with different cut-off points of diagnosis. Multivariate analysis showed that clinical status and toothbrushing frequency were statistically significantly associated with self-assessed gingival bleeding in both tests. Socioeconomic status and locus of control orientation were also statistically significant factors in the toothpick test. In conclusion, the validity of self-assessment of bleeding was sufficient for monitoring adolescents' gingival health in groups. Self-assessed bleeding was explained by the same factors that were associated with clinical gingival health status.