Background: Abortion is legal up to 12 weeks’ gestation period in Nepal. Due to a lack of proper abortion services and socio cultural stigma, every year many women died due to abortion. The aim of this study was to asses the knowledge, attitude and practice of abortion in the residents of slum area of Kathmandu district. Methods: The cross-sectional study was conducted in slum area of Kathmandu district from 20th December, 2020 to 15th January, 2021. The sample size was 255 and convenient sampling technique was used to select the participant aged above 15years. The collected data were enter in MS excel and analysis was performed using SPSS version 22. Results: The prevalence of abortion was 25.27%.The level of knowledge was found significant with education status. Age, marital status, ethnicity were found significant with attitude of the respondents. Ten percentages of the female respondents had done unsafe abortion. The complications after abortion were the bleeding (54.3%), trauma (15.20%), loss of consciousness (13.0%) and abdominal pain (2.20%). Conclusions: The level of knowledge of participants of the present study found to be satisfactory but attitude was less satisfactory with compared to the knowledge about the abortion.