Objective ICU severity scores such as the Sequential Organ Failure Assessment (SOFA) determine neurologic dysfunction based on the Glasgow Coma Scale, a tool that may be limited in a critically ill population. It remains unknown whether alternative methods to assess for neurologic dysfunction, such as FOUR and RASS, are superior. This study aimed to determine the predictive performance of a modified SOFA tool in a large Brazilian ICU cohort. Design Prospective cohort single center study. Setting Mixed surgical and medical ICU in Salvador, Bahia, Brazil between August 2015 and December 2018. Patients All acutely ill ICU admissions, other than postoperative patients or those with insufficient data, were eligible for study inclusion. Measurements and main results 2147 patients were admitted to the ICU, of which 999 meeting inclusion criteria were included in the final analysis with a median age of 72 years (IQR 58–83) and a female predominance 545 (54%). The SOFA score using GCS, RASS and FOUR for the neurologic component performed marginally in the ability to predict general ICU mortality (SOFAGCS AUC 0.74 vs SOFARASS AUC 0.71 and SOFAFOUR AUC 0.67), with SOFAFOUR performing significantly lower compared to either SOFARASS and SOFAGCS (p<0.04, p<0.004 respectively). All three scores demonstrated decreased discriminate function in the mechanically ventilated population (SOFAGCS AUC 0.70 vs SOFARASS AUC 0.70 and SOFAFOUR AUC 0.55), though SOFAFOUR remained significantly worse when compared to SOFAGCS or SOFARASS (p = 0.034, p = 0.014, respectively).. Furthermore, performance was poor in a subset of patients with sepsis (n = 145) at time of admission (SOFAGCS AUC 0.66 vs SOFARASS AUC 0.55 and SOFAFOUR AUC 0.56). Conclusion Modification of the neurologic component in the SOFA score does not appear to improve mortality prediction in the ICU.