BACKGROUND The reference intervals (RIs) for the renal biomarkers urea and creatinine, in Greyhounds, are higher than those for non-sighthound breeds. A recent study has demonstrated a higher concentration of another biomarker of renal function, symmetric dimethylarginine (SDMA), in Greyhounds compared with other dog breeds, and thus a breed-specific RI for serum SDMA may be appropriate for Greyhounds. Greyhounds appear to be predisposed to renal disease, and the establishment of an appropriate RI for SDMA may improve the ability to identify early renal dysfunction in this breed. OBJECTIVE The aim of this study was to establish an RI for serum SDMA in nonracing Greyhounds and to determine whether the RI for Greyhounds is different from that of non-sighthound breeds. METHODS Blood samples were collected from 101 clinically healthy, nonracing Greyhounds for serum SDMA measurements. Results from Greyhounds were compared with serum SDMA concentrations measured in a group of non-sighthound dogs (n = 24) of similar weight, age, and sex, and with a previously established canine serum SDMA RI. RESULTS The serum SDMA RI for Greyhounds was 6.3-19.9 μg/dL (0.31-0.99 μmol/L). Greyhounds had a significantly higher mean value (13.1 μg/dL) than that of the non-sighthound dogs (10.2 μg/dL) (P < .001), and the RI of Greyhounds was different from previously established canine RIs for SDMA. CONCLUSIONS This study supports the use of a Greyhound-specific RI for SDMA. Using previously established canine RIs for this breed could result in the overdiagnosis of renal disease.