Public service motivation (PSM) research heavily relies on self-report measures that are often susceptible to social desirability bias (SDB). Cultural orientation is also correlated with SDB. This study explores the ethnic differences in socially desirable responding when measuring PSM and job satisfaction in a multicultural but individualistic society like the United States. It tests the magnitude and pattern of SDB in measurements of PSM in this society as a whole, as well as the influence of ethnicity on SDB. The results of our experimental survey research show that SDB is significantly correlated with PSM measures, as well as job satisfaction. We therefore expect a spurious effect to occur in the correlational analysis. This implies that the correlation between job satisfaction and PSM is at least partly spurious due to measurement artifacts. Alternative ways to measure PSM need to be explored to control SDB.