Objectives Fatty acids (FAs) have various roles in pro-inflammatory and anti-inflammatory functions. Hypoalbuminemia is often observed in sepsis patients. An imbalance among these compounds formed from FAs caused by hypoalbuminemia may be related to increased mortality in sepsis patients. The purpose of this study was to investigate the correlations between serum albumin and FAs in sepsis and the outcome. Methods This study was an observational investigation. The clinical and laboratory data of sepsis patients were recorded and the Sequential Organ Failure Assessment (SOFA) score was calculated at admission. The serum arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and dihomo-gamma-linolenic acid (DHLA) levels were also measured as FAs. The body mass index (BMI) was used to determine the general nutrition status. Results Two hundred sepsis patients were enrolled during the study period. No significant correlations were observed between the BMI and the SOFA score or the serum albumin level at admission. The FA levels of the non-survivors were significantly lower, but there were no significant differences in the EPA/AA levels of the survivors and non-survivors. A low serum albumin level was closely related to low AA (p<0.0001), EPA (p<0.0001), DHA (p=0.0003), and DHLA levels (p<0.0001). A multiple logistic-regression analysis revealed that a high SOFA score [adjusted odds ratio, 1.19; 95% confidence interval (CI), 1.02-1.39, p=0.026] and low AA (adjusted odds ratio, 0.98; 95% CI, 0.978-0.994, p=0.041) were associated with a poor outcome. Conclusion A lower AA level was an important determinant of the outcome of patients with sepsis. These findings are consistent with the findings of previous studies, which reported that hypoalbuminemia might alter the AA metabolism in sepsis patients.