Introduction: A study to assess the knowledge of nurses regarding care of patients on mechanical ventilator support. The purpose of this study was to determine the knowledge of nurses working in tertiary level hospital about care of patients on mechanical ventilator. Nurses are taking care of a patient on ventilator. They should have adequate knowledge regarding ventilator care for maintaining adequate standards of care. Objectives: The objective of this study was to assess the knowledge about care of patients on mechanical ventilator among nurses working in tertiary level hospital. Method:A descriptive study of nurses in tertiary level of hospital was done by administering structured questionnaire. Hundred samples were selected by using convenience sampling. The duration of the study was from January- March 2019. Results: In this study 20 item survey include specific questions about care of patient on ventilator. Study shows that 13% of nurses have very high knowledge, 73% have high knowledge 13% have average and 1% have low knowledge. The mean knowledge was 13.92+ (2.18). Conclusion: This study shows that nurses have high knowledge regarding care of patient on ventilator support.