Background: The purpose of this study was to determine the prevalence and related factors of low birth weight (LBW) in the Southeast of Iran. Methods: This cross-sectional study was carried out in Kerman province. Data were collected from Iranian Maternal and Neonatal Network at public and private hospitals. All live births from March 2014 to March 2015 considered as the source population. The risk factors including maternal age, gravida, parity, abortion, pregnancy risk factors, maternal nationality, maternal education, maternity insurance, place of living, consanguinity, neonate sex, preterm labor, place of birth, delivery manager, and delivery type were compared between LBW and normal birth weight groups. Results: The prevalence of LBW was 9.4% in the present study. Preterm labor (odds ratio [OR]: 22.06; P < 0.001), neonate female sex (OR: 1.41; P < 0.001), low parity (OR: 0.85; P < 0.001), pregnancy age <18 years (OR: 1.26; P = 0.012), pregnancy age >35 years (OR: 1.21; P = 0.001), delivery by cesarean section (OR: 1.17; P = 0.002), pregnancy risk factors (OR: 1.67; P < 0.001), maternal illiteracy (OR: 1.91; P < 0.001), living in the rural area (OR: 1.19; P < 0.001), consanguineous (OR: 1.08; P = 0.025), and delivery by obstetrician (OR: 1.12; P = 0.029) were identified as significant factors associated with LBW in this study. Conclusions: Prevention of preterm labor, consanguineous marriage, pregnancy age <18 and >35 years old, and maternal medical risk factors are some critical interventions to reduce its burden. Increasing the access to high-quality health-care services in rural and deprived areas is another effective strategy for the prevention of LBW.