The age at first birth is very low under existing rural sociocultural settings in Bangladesh. This study examined the socioeconomic and cultural determinants of age at first birth. The study subjects were married women aged 15 to 29 years in 2 rural areas that were identified through a multistage sampling technique. To collect the relevant information, a semistructured interviewer schedule was applied to the eligible women. This study found that 72.8% women gave first birth at <20 years of age with mean age at first birth 18.74 years. Simple linear regression model explained 30.9% of variance in age at first live birth. Among socioeconomic and cultural determinants, family pressure explained the most significant variance. It is really difficult to reduce fertility in complex sociocultural settings in rural Bangladesh. However, the findings of this study may provide an answer to increase the age at first birth and hence to reduce the high fertility among these group of women.