Background: Developing effective trauma scoring systems are critical to helping improve trauma outcomes. The New Injury Severity Score (NISS) has emerged as an important trauma scoring system validated in developed countries, however its usefulness in resource challenged developing countries has not been fully evaluated. Aims: To determine the pattern and outcomes of abdominal trauma in patients presenting to Lagos University Teaching Hospital (LUTH), and to evaluate the usefulness of the NISS in predicting mortality and other secondary outcomes in these patients. Method: The study recruited all consenting patients aged 16years and above presenting with abdominal trauma to LUTH over a 1 year period. Demographic data, injury to presentation time, surgical intervention time, injuries sustained were recorded and the NISS scores were calculated for the patients. The patients were managed as appropriate and outcome was evaluated at the end of 30days. The value of the NISS in predicting mortality and other outcomes such as ICU admission, complications and residual morbidity were evaluated using the Area under Curve (AUC) of the Receiver Operating Characteristic (ROC) curve. Results: 83 patients were recruited (71 males, 12 females). 42 patients had penetrating abdominal trauma while 41 patients had blunt abdominal trauma. The mean duration from injury to presentation was 11 hours, while the mean surgical intervention time was 31 hours. There were 12 mortalities (14.1%). The NISS performed excellently in predicting mortality, with an AUC of 0.952. It also performed very well in predicting ICU admission (AUC: 0.876). It did not perform so well in predicting development of complications (AUC: 0.789). It showed no value in predicting residual morbidity at 30 days (AUC of 0.548). Conclusion: The NISS is an excellent predictor of mortality and ICU admission in patients with abdominal trauma in this environment. However, it is not so useful in predicting complications, and has no value in predicting residual morbidity.