jats:titleAbstract</jats:title>jats:secjats:titleBackground</jats:title>jats:pSerum symmetric dimethylarginine (SDMA) concentrations are considered a biomarker for renal dysfunction in dogs and humans with acute kidney injury (AKI). No studies have assessed SDMA in cats with AKI.</jats:p></jats:sec>jats:secjats:titleHypothesis/Objectives</jats:title>jats:pSDMA correctly identifies cats with azotemic AKI.</jats:p></jats:sec>jats:secjats:titleAnimals</jats:title>jats:pFifteen control cats, 22 with novel AKI, 13 with acute on chronic‐AKI (AoC) and 19 with chronic kidney disease (CKD).</jats:p></jats:sec>jats:secjats:titleMethods</jats:title>jats:pRetrospective study. Cats with azotemia (serum creatinine concentrations >1.7 mg/dL) were defined as having AKI or CKD based on history, clinical signs, clinicopathological findings and diagnostic imaging, and classified using the International Renal Interest Society (IRIS) grading/staging systems. Serum SDMA concentrations were compared between groups with nonparametric methods, and correlations assessed using Spearman's correlation coefficient. Data are presented as median [range].</jats:p></jats:sec>jats:secjats:titleResults</jats:title>jats:pSDMA concentrations were 11 (8‐21) μg/dL, 36 (9‐170)μg/dL, 33 (22‐75) μg/dL and 25 (12‐69) μg/dL in control, novel AKI, AoC and CKD cats. SDMA concentrations were significantly higher in cats with novel AKI (jats:italicP</jats:italic> < .001), AoC (jats:italicP</jats:italic> < .001) and CKD (jats:italicP</jats:italic> < .01) compared to controls. SDMA concentrations were significantly higher in cats with more advanced AKI (IRIS grade IV‐V) compared to less severe AKI (IRIS grade II). Serum creatinine and SDMA concentrations had a significant correlation in cats with novel AKI (jats:italicr</jats:italic>jats:subs</jats:sub> = 0.826, n = 22; jats:italicP</jats:italic> < .001) and a significant correlation when all cats across all 4 groups were considered together (jats:italicr</jats:italic>jats:subjats:italics</jats:italic></jats:sub> = 0.837, n = 69; jats:italicP</jats:italic> < .001).</jats:p></jats:sec>jats:secjats:titleConclusions and Clinical Importance</jats:title>jats:pSerum SDMA concentrations are elevated in cats with established AKI (novel and AoC) and CKD, providing evidence for use of SDMA as a biomarker for AKI in cats.</jats:p></jats:sec>