Rationale and Background: : Breastfeeding (BF) is considered an effective way to provide balanced nutrition, better growth, and development of the infant, prevent stunting as well as protect from infectious and chronic diseases. WHO and UNICEF recommended exclusive BF (EBF) for the first six months of age and giving no other food or drink to the infant during this period. The government of Lao PDR has launched several strategies and policies in an effort to improve exclusive breastfeeding since 2006. The EBF Campaign was strongly promoted during 2009-2010 to improve child survival rates and enhance the development of children by increasing the number of mothers who EBF their newborn for six months. Methodology: : This study was conducted in two provinces in Lao PDR. A cross-sectional analytical study design was applied in this study to examine the prevalence of EBF duration and identify the factors associated with EBF duration. The sample size estimation was 710 mothers. Probability random sampling using a multi-stage sample technique was used. Data were collected through a face-to-face interview in the household. The median duration and 95% CI of BF was derived using Kaplan-Meier survival curves, and multivariable Cox proportional hazards (PH) models were performed. Results: : Out of 710 mothers, the age of study participants was between 15 and 45 years; the mean age and SD were 27.3 ± 5.8 years, and almost all of them (97.2%) were married. 75.4% members were Lao Ethno-linguistic group, 50.8% were educated at high school, and 43.1% of participants were housewives. 53.3% of her husbands stayed at high school, and 49.4% of them took on the occupation of farmer or agriculturalist. 57.9% were classified as exclusive breastfeeding; the median duration of breastfeeding was 12 months; 40.1% were breastfeeding for 7–12 months. Factors significantly associated with breastfeeding duration included the number of prior pregnancies, age at first pregnancy, whether a postnatal check was conducted after hospital discharge or home birth, child’s weight, and child’s height. Conclusion: Breastfeeding duration is influenced by a variety of factors, including the number of previous pregnancies, age at first pregnancy, postnatal health check-ups, the child's weight, and maternal knowledge about breastfeeding. Understanding and addressing these factors is crucial in promoting successful and sustained breastfeeding among mothers, ultimately leading to improved health outcomes for both mothers and children.