This study examined awareness of unwanted pregnancy, abortion behaviour, methods and attitudes toward specific legal indications for abortion via a school-based internet survey among 378 adolescents aged 12–21 years in three Rio de Janeiro public schools. Forty-five percent of those surveyed knew peers who had undergone an abortion. Most abortion methods (79.3%) reported were ineffective, obsolete, and/or unsafe. Herbs (e.g. marijuana tea), over-the-counter medications, surgical procedures, foreign objects and blunt trauma were reported.  The study concluded that abortion knowledge and attitudes are not driven simply by age, religion or class, but rather a complex interplay that includes both social spaces and gender. Prevention of abortion morbidity and mortality among adolescents requires comprehensive sexuality and reproductive health education that includes factual distinctions between safe and unsafe abortion methods.