Background and objective Sepsis is a major health burden that leads to significant morbidity and mortality. Early diagnosis and severity prediction using various scoring systems can reduce the mortality rate, particularly in developing nations. There are two aims of this study. One is to evaluate the prognostic accuracy of the Sequential Organ Failure Assessment (SOFA) score and serum lactate levels in patients with sepsis to predict mortality. The other aim is to evaluate the relationship between the SOFA score and lactate so that we may be able to use lactate as a surrogate predictor of organ dysfunction and mortality in sepsis. Methods An observational prognostic accuracy study was conducted in the Department of General Surgery, Intensive Care Unit (ICU), Rajendra Institute of Medical Sciences (RIMS), Ranchi, Jharkhand, India, between 1July 2021 and 1 October 2022. We selected 128 patients, calculated their SOFA and lactate levels, and divided them into survivors and non-survivors according to their outcomes after seven days of assessment. The SOFA score and serum lactate levels were assessed as predictors of mortality, and their correlation was studied. Results We observed a significant decreasing trend in the value of the mean SOFA, maximum SOFA, mean lactate, and maximum lactate among survivors, whereas an increasing trend for the same was observed in non-survivors. The receiver operating characteristic (ROC) analysis showed the best diagnostic accuracy of the mean lactate (area under the curve {AUC}=0.996, 95% confidence interval {CI}=0.964-1.00, p≤0.0001). The maximum lactate (AUC=0.987, 95% CI=0.949-0.999, p≤0.0001) and mean SOFA scores (AUC=0.986, 95% CI=0.948-0.999, p≤0.0001) were good at predicting the mortality in sepsis. A slightly lower diagnostic accuracy was found for the maximum SOFA score (AUC=0.969, 95% CI=0.923-0.992, p≤0.0001). There was a strong correlation between the mean lactate and the mean SOFA with a correlation coefficient of 0.883 and p=0.0001. A good correlation was found between maximum lactate and maximum SOFA too (correlation coefficient=0.873, p≤0.0001). Conclusion This study highlights the different predictors of mortality in the patients with sepsis. The maximum lactate was the most accurate in predicting mortality in sepsis. It also demonstrates how serum lactate, due to its strong correlation with the SOFA score, can be used in its place to predict mortality in sepsis and organ dysfunction.