Objectives: To investigate whether lipopolysaccharide (LPS) is present in plasma of calves with naturally occurring diarrhea. The second objective was to determine whether plasma [LPS] correlates with clinical, hematological, biochemical, and acid-base variables, and whether [LPS] differs between surviving and nonsurviving diarrheic calves. Design: Prospective observational study (January 2012–May 2014). Setting: Veterinary teaching hospital. Animals: Thirty-four calves <28 days old admitted for diagnosis and treatment of diarrhea and 30 healthy control calves. Measurements and Main Results: Admission demographics, physical examination, blood gas, biochemistry analysis, and outcome data were recorded. Plasma concentration of LPS was determined using a bovine LPS ELISA assay. Plasma [LPS] was detected in both healthy and diarrheic calves. Plasma [LPS] was significantly higher in diarrheic than healthy calves (median: 0.99 ng/mL; Interquartile range (IQR): 0.068, vs 0.88 ng/mL; 0.065 ng/mL, respectively; P < 0.001). Plasma [LPS] was higher in nonsurviving (1.04 ng/mL; 0.07 ng/mL) than in surviving calves (0.98 ng/mL; 0.022 ng/mL; P < 0.001). Plasma [LPS] was higher in beef (1.07 ng/mL; 0.182 ng/mL) than in dairy diarrheic calves (0.99 ng/mL; 0.022 ng/mL; P < 0.001). In diarrheic calves, plasma [LPS] correlated with [l-lactate] (r 2 = 0.496; P = 0.002); hypoglycemia (r 2 = −0.453; P = 0.007); increased unmeasured strong ions (r 2 = 0.332; P = 0.050), [Mg 2+ ] (r 2 = 0.475; P = 0.004), and [phosphate] (r 2 = 0.468; P = 0.005), and increased aspartate aminotransferase activity (r 2 = 0.348; P = 0.003). Conclusions: This study highlights a potential role of LPS in the pathogenesis of metabolic derangements such as hyperlactatemia, hypoglycemia, and increased concentration of unmeasured strong anions in diarrheic calves. Further investigation evaluating the effect of LPS on l-lactate and glucose metabolism in diarrheic calves is warranted.