The Pap smear is a reliable, inexpensive and effective screening test for cervical cancer; the second most common cancer among women worldwide. We aimed to determine women's knowledge, attitudes and practice towards Pap smear in women live at the northwest of Tehran city. This study, was carried out on 334 outpatient Iranian women in winter 2018. A questionnaire including demographic characteristics (10 questions), knowledge (10 questions), attitudes (5 questions) and practice (2 questions) towards Pap smear was completed by an interview with the women. The data were analyzed using SPSS ver22. The mean age of all participants was 36.59 ± 15.409 years. 52.4% had performed the Pap smear test, 24.3% of which performed Pap smears regularly the knowledge level of participants who had done Pap smear was low at 28.6%, moderate at 55.4%, and high at 16.0%. The knowledge level of participants who did not perform Pap smear was low at 41.5%, moderate at 49.7%, and high at 8.8%. The attitude of the participants to Pap smear was undesirable in 1.2%, moderate in 3%, and 98.8% desirable. The attitude of the participants who had done Pap smear was undesired in 4.2% of the subject, moderate in 15%, and desired in 80.8 and in another group was 15.5%, 56.7% and 27.8% respectively. The knowledge and practice of the women were inadequate and needed to be promoted. Considering the main reason mentioned by the participants for not having the test, all health providers should educate and encourage women to do regular Pap smear.