Objective: To know the prevalence of low birth weight and its association with socio demographic and maternal factors in Tertiary care Hospital, Tirupati. Settings: Government Maternity Hospital attached to S.V. Medical College, Tirupati Study design: Hospital based cross sectional study Participants: 1200 postnatal women who delivered single live baby in the Government Maternity Hospital, Tirupati. Methodology: Systemic random sampling Study Period: January 2011 to December 2011 Statistical analysis used: Chi-square test and binary logistic regression analysis Results: Prevalence of Low birth weight was 26.8%. The prevalence of low birth weight was high and significant in less than 20 years of age group (42.0%), illiterate mothers (37.4%), occupation as labor (27.4%), low income (28.5%), consanguinity history (38.7%), primigravida (29.8%), women of birth order 3 and above (33.3%), narrow birth interval (34.8%), gestational age less than 37 weeks (72.7%), weight gain less than 6 kgs (57.7%), height less than 145cms (51.0%), weight less than 45kgs (55.2%), low hemoglobin level, less than 3 ante-natal checkups (87.5%), IFA tablets not consumed or less than 50 tablets during pregnancy (48.0%), hard physical labor during pregnancy (56.4%), tobacco chewing (44.7%), female babies (30.6%) and obstetric complications during pregnancy (50.4%). sHowever residence of mother showed any significant effect on low birth weight. Conclusion: To emphasize on need of improving ante natal coverage as well as quality of services.