Introduction: Malnutrition is an emerging but neglected problem in hospitalized surgical patients which contributes significantly to the adverse postoperative outcomes. However, in most of our settings; patients scheduled for abdominal surgeries are not routinely assessed for nutritional status rendering difficultness in mitigating the avoidable predicaments. Objective: To determine the prevalence of malnutrition and its association with the early outcomes among patients undergoing abdominal surgery at Bugando Medical Centre (BMC), Mwanza, Tanzania. Methods: This was a prospective longitudinal study involving adult patients who underwent abdominal surgeries at BMC from January 2023 to June 2023. Nutritional status assessment was done according to the Nutrition Risk Screening tool (NRS-2002). Results: The overall prevalence of malnutrition was found to be 51.8%. Complication and mortality rates were 25.4% and 8.3% respectively. The overall length of hospital stay ranged from 5 days to 14 days (median of 9 days). Preoperative malnutrition was found to be statistically significant associated with early postoperative complications (OR=4.1, 95% [2.0-8.2], p-value< 0.001), prolonged Length of hospital stay (LOS) (OR=2.5, 95% [1.4-5.8], p-value = 0.003) and mortality (OR=4.6, 95% [2.5-11.2], p-value < 0.001). Furthermore, preoperative malnutrition significantly predicted surgical site infections (OR=2.2, 95% [1.0-4.8], p-value =0.047) and anastomotic leakage (OR=3.1, 95% [1.1-8.9], p-value =0.035). Conclusion: Preoperative malnutrition is a significant and independent risk factor for postoperative complications, prolonged hospital stay and mortality following abdominal surgery. This study emphasizes the need for routine assessment of nutritional status using a validated tool preoperatively so as to draft a nutrition care strategy to prevent postoperative malnutrition-related adverse outcomes.