National Injury Surveillance System which was initiated in Base and above Hospitals is one of the main strategies identified in the national policy and strategic framework on injury prevention in Sri Lanka. However, the overall coverage of In-Patient component of National Injury surveillance (ICNIS) in these hospitals was 14 %. Hence, this study was aimed at identifying factors affecting ICNIS in Base Hospital Karawanella. The study was carried out by mapping the existing process, Focus Group Discussions and Key Informant Interviews with relevant staff and desk review of randomly selected 184 Bed Head Tickets (BHT) with Injury Surveillance Forms (ISF) of patients discharged during five months in 2019. The study revealed that coverage of capturing of patients in ICNIS was 7.2% and timeliness of data entry to the system (within 30 days of patient discharge) is 11%. Completeness and Accuracy of most of the captured data in ISF are above 80%. Lack of capacity building, unavailability of access to hospital data in the system, poor feedback mechanism, disagreement of staff on issuing and filling ISF and poor monitoring mechanism are the other factors identified. Streamlining of the process of ICNIS by issuing and filing ISF at multiple entry points, amending the current circular and guide enabling Nursing Officers to fill ISF under the guidance of MO, simplifying ISF, arranging periodic in-service training and providing uninterrupted access to EIMMR system with an analytical module at all hospitals.