Background: The number of people newly infected with human immunodeficiency virus (HIV) has been decreasing in sub-Saharan Africa, but prevalence of the infection remains unacceptably high among young people. Despite the alarming pervasiveness of the virus, young people in this region continue to engage in risky sexual behaviors including unprotected sexual intercourse. In developed countries, parents can play important roles in protecting young people from such behaviors, but evidence regarding the impact of parental involvement is still limited in sub-Saharan Africa. Therefore, we conducted this study to examine the magnitude of risky sexual behaviors and the association of parental monitoring and parental communication with condom use at last sexual intercourse among secondary school students in Dar es Salaam, Tanzania. Methods: We conducted this cross-sectional study among 2,217 male and female students aged 15 to 24 years from 12 secondary schools in Dar es Salaam. From October to November 2011, we collected data using a self-administered questionnaire. Multiple logistic regression analyses were conducted to examine the association of parental monitoring and parental communication with condom use at last sexual intercourse, adjusting for potential confounders. Results: A total of 665 (30.3%) secondary school students reported being sexually active within the year prior to data collection. Among them, 41.7% had multiple sexual partners, 10.5% had concurrent sexual partners, and 41.1% did not use a condom at last sexual intercourse. A higher level of parental monitoring was associated with increased likelihood of condom use at last sexual intercourse among male students (AOR: 1.56, 95% CI: 1.05-2.32; p = 0.03) but not among female students (AOR: 1.54, 95% CI: 0.71-3.37; p = 0.28). The association between parental communication and condom use at last sexual intercourse among both male and female students was not statistically significant. Conclusions: A high level of parental monitoring is associated with more consistent condom use among male students in Dar es Salaam, Tanzania – many of whom have engaged in high-risk sexual behaviors such as multiple sexual partnerships, concurrent sexual partnerships, and unprotected sexual intercourse in the past one year. Interventions should thus be strengthened to reduce multiple sexual partnerships, concurrent sexual partnerships, and to improve parental monitoring among such students toward increasing condom use