Background: One of the most important etiologies in pretermpremature rupture of membranes (PPROM) is cervical bacterial colonization. Objective: This study evaluated cervical bacterial colonization in women with PPROM and the pregnancy outcomes. Materials and Methods: In this cohort study, 200 pregnant women with PPROM at27-37 wk of gestation who were admitted in an academic hospital of Mashhad University of Medical Sciences from March 2015 to July 2016 were studied. samples were obtained from endocervical canal for detection of routine bacteria and Gram staining. Also, we obtained one blood culture from neonates. Maternal endocervical culture, chorioamnionitis, neonatal intensive care unit admission, neonatal positive blood culture, neonatal sepsis, and mortality were documented. Results: Most common isolated microorganism of endocervical culture were Escherichia coli (24.2%), Coagulase negative Staphylococci (27.2%), Enterococcus and candida each one (11.7%). The prevalence of GBS was only 2.2%. Simultaneous positive blood cultures were seen in 3% of neonates. Among them, Gram-negative bacilli accounted for (66.6%), while Gram-positive cocci and candida made up only (16.7%). Endocervical colonization was associated with a higher admission rate (p=0.004), but there was no significant correlation between endocervical colonization and chorioamnionitis, positive blood culture and neonatal mortality rate. Conclusion: With regard to low GBS colonization rate, appropriate antibiotic regimens should be considered in PPROM cases according to the most prevalent micro organisms of endocervical bacterial colonization. Maybe cervical bacterial colonization had some effects on neonatal outcomes. There was no significant association between endocervical bacterial colonization and chorioamnionitis, positive neonatal blood culture and neonatal mortality.