Preliminary Care Unit is the Sri Lankan model of the emergency department in the state health facilities above the level of Base Hospitals in the country. Provision of prompt, quality, and comprehensive patient care without any unnecessary delay, minimizing unnecessary admissions to wards, and reducing the cost of patient management were the objectives of establishing such units. The current study aimed to systematically assess the process of service delivery in the Preliminary Care Unit of District General Hospital, Gampaha. The study was descriptive with both cross-sectional and retrospective components and was conducted in 2019. Study instruments and techniques included are key informant interviews, focus group discussions, the desk review of secondary data, and direct observation. Key informant interviews with the medical officer-in-charge and nursing sister in charge of the unit were conducted by the principal investigator. Two focus group discussions were conducted, with ten randomly selected medical officers and 8 nursing officers with a minimum one-year of work experience at the Preliminary Care Unit. Data gathered from the desk review of the secondary data from the admission book, Bed Head Tickets, and record of monthly statistics of the preliminary care unit using a checklist to ascertain the total number of admissions and their outcome in 2018. All admissions of a randomly selected week of 2018 were studied to assess the age and gender distribution and they were classified into two categories as medical and surgical, according to the admitting doctor’s notes. Direct observation was used to triangulate the data. The major deficiencies of the process of service delivery in the Preliminary Care Unit elicited at the key informant interviews and focus group discussions were overcrowding and excess waiting which were multifactorial in causation. Less organized process flow and inadequate resource availability led to overcrowding and excess waiting.