Introduction: Nosocomial infections are those infections acquired as a result of treatment in a hospital or health care service providing center so they are also known as hospital-acquired infections(HAI). Nosocomial infections usually encountered include urinary tract infection, respiratory tract infection and Enterococci infections. Objectives: Study was focused on determining the various nosocomial infection occurring in tertiary care hospital, common microorganisms involved in causing nosocomial infection and commonly used antibiotic for treatment of nosocomial infections. Methodology: This was a prospective, cross-sectional, and observational study carried out in different wards and departments of a tertiary care hospital for a period of six months. Patients data was collected from the inpatient profile form, patient history records, laboratory data. Results: A total number of 100 subjects included from different wards to evaluate the study. The percentage of male subjects and female subjects was calculated 42% and 58% respectively. all the subjects were found below the age of 75 years, maximum subjects(35%) were found in age group of 20-40 years. The obtained data shows that most of the subjects were infected by gram-negative microorganism(80%), maximum number of cases were found infected with urinary tract infection(52%), followed by surgical site infection(43%), neonatal infection(3%) and respiratory tract infection(2%). The common microorganisms involved in causing nosomial infections was Escherichia coli(44%), Enterococcus spp.(15%), Enterobacter spp.(28%). Antibiotics such as nitrofurantoin, cefoperazon+sulbactum, amikacin were mostly used for the treatment of various nosocomial infections. Conclusion: It was concluded that gram-negative and gram-positive pathogens were responsible for majority of nosocomial infections occurring in a tertiary care hospital. In the study, maximum number of cases were found infected with urinary tract infection, followed by surgical site infection. The most common bacteria found was Escherichia coli, Enterobacter spp., Enterococcus spp. Most effective antimicrobial agent for gram-negative pathogens wereimepenem, nitrofurantoin and amikacin and for gram-positive pathogens was linezolid.