The constructing laborers are mainly unskilled, untrained, migrant, socially backward, and uneducated with low bargaining power. Thus, we assessed the knowledge and prevalence on occupational safety and health (OSH) of laborers working at private constructing sites. A descriptive cross-sectional study of 229 laborers working at private constructing sites selected by 30 cluster sampling methods from the Lalitpur metropolitan city and Mahalaxmi municipality was conducted using a structured questionnaire and observation checklist. EpiData and SPSS were used for data analysis. Most of the laborers (62%) had inadequate knowledge on OSH. The level of knowledge was significantly associated with sex, education, and family type at 95% CI (p value < ...