The treatment modality of gastric adenocarcinoma (GCA) depends on the stage of the disease at the clinical presentation. Long delays are probably an unfavorable factor for the patient's prognosis. A prospective longitudinal, study involving 145 consecutive GCA was conducted at the National Hospital of Sri Lanka (NHSL). The overall delay (in weeks) was recorded for each patient and divided into four periods-patient, endoscopy, pathology and treatment. The median and Interquartile Range (IQR) duration of delays were calculated and differences were explored with chi square test and Mann Whitney U test Survival analysis was done with Kaplan Meier technique and Cox regression. The median duration of delays for patient, endoscopy, histology reporting delay, other histology delay (specimen transfer delay and report receipt delay) and treatment were 18 (IQR 14–27), 2 (IQR 2–3), 3 (IQR 2–3), 2 (IQR 1–2) and 6 (IQR 4–8) weeks respectively. Delayed patient presentation to hospital was associated with significant adverse median survival 16 (IQR 11.5–22.5) weeks versus 20 (IQR 16–27.5) weeks, p = 0.004. Delay in initiating treatment was associated with significantly lower median survival 04 (IQR 4–6) weeks versus 06 (IQR 4–8) weeks, p = 0.003. Over 60% of both proximal and distal GCA presented at an advanced radiological stage (stage III/IV). The Kaplan Meier analysis showed that the higher hazard function was associated with a higher tumour stage and undergoing chemotherapy. Age of the patient and the treatment modality were significant predictors of the survival. Patient delay and delay in initiation of definitive treatment are the most important factors that adversely affect the outcomes of GCA. Public health interventions aiming to shorten the patient delay time with proper referral for specialist care would play an important role. Also, it is important to minimize these preventable delays and there should be time limits in producing the histopathology report and to establish online portals of hospital and laboratory information systems for easy access of histology reports in future.