The purpose of this study was to determine the prevalence of depression, anxiety and suicide ideation among pregnant adolescents and verify the relationship between suicide ideation and other variables. 120 pregnant adolescents (40 in each gestational trimester) attended at a public health center in Brazil were assessed. The following research instruments were used: the Clinical Interview Schedule (CIS-R), the Hospital Anxiety and Depression scale (HADS) and the Beck's Suicide Ideation Scale (BSI). The Chi-square test, the Fishers and the Mann-Whitney U tests were performed. There were 28 cases of anxiety (23.3%), 25 (20.8%) of depression and 20 cases of suicide ideation (16.7%). There was no difference in these prevalences in the gestational trimesters. There was a significant relationship between suicide ideation suicide and depression (p = 0.001), single individuals without boyfriends (p = 0.01) and little social support ( p = 0.001). Cases of suicidal ideation presented a high frequency of lack of concentration, anxiety, depression, preoccupations, obsessions, depressive ideas, tiredness, worries concerning body functions and compulsions. The group of pregnant adolescents showed heterogeneous results regarding mental health. The most common symptom of depression, anxiety, ideation suicide and previous suicide attempts were depressive ideas. The health professionals working with pregnant adolescents should observe them carefully, in order to detect the presence of depressive ideas.48245-9