Background Sepsis is a potentially fatal condition that necessitates prompt identification and assessment of its severity for effective management. However, evaluating sepsis severity using the Sequential Organ Failure Assessment (SOFA) and Acute Physiology and Chronic Health Evaluation (APACHE II) scores can be complex and costly. This study aimed to assess the association between neutrophil-to-lymphocyte ratio (NLR) and sepsis severity, as well as the role of NLR as a predictive indicator of sepsis severity in ICU patients. Methods This cross-sectional study was conducted among 180 ICU-admitted patients at Benazir Bhutto Hospital (BBH) in Rawalpindi, Pakistan, from January 2022 to January 2023. Participants were enrolled using defined inclusion and exclusion criteria along with consecutive sampling. Following ethical approval and informed consent, data were collected using a self-structured form. The study population was divided into three groups based on sepsis severity, which was assessed via the SOFA score. Data analysis was performed using IBM SPSS Statistics for Windows, Version 25.0 (Released 2017; IBM Corp., Armonk, NY, USA) through chi-squared tests, one-way ANOVA, Pearson's correlation, and a simple linear regression model, with a significance threshold set at p < 0.05. Results In the study population of 180 patients, the frequencies of sepsis, severe sepsis, and septic shock were 69 (38.34%), 86 (47.78%), and 25 (13.88%), respectively. Significant variations were observed among the three study groups in the means of the PaO2/FiO2 ratio, mean arterial pressure, Glasgow Coma Scale score, total bilirubin level, serum creatinine level, platelet count, SOFA score, neutrophil count, lymphocyte count, and NLR (p < 0.05). Pearson's correlation analysis indicated a strong positive correlation between the NLR and SOFA score, with a correlation coefficient (r) of 0.80 and significance at p < 0.001. Furthermore, linear regression analysis identified NLR as a significant predictor of sepsis severity, with a beta coefficient (β) of 3.55 and a 95% CI of 1.92-5.60 (p < 0.001). Conclusions In the current study, a positive and significant correlation was found between the NLR and the severity of sepsis. Higher NLR values were associated with increased SOFA scores, indicating a greater severity of sepsis. This study supports the use of NLR as a complementary and cost-effective tool for the early detection of high-risk patients with sepsis, facilitating timely interventions and improving outcomes, particularly in under-resourced healthcare settings.