A large body of literature demonstrates that East Asian women report lower sexual desire than Caucasian women. Although most studies have explained these differences by referring to general culture-linked differences in sexual conservatism, none have examined the potential role of specific constructs such as sex guilt. The goals of the current study were to examine the supposition that sexual conservatism mediates the relationship between culture and sexual desire, and to explore the potential mediating role of sex guilt in the link between culture and sexual desire. Caucasian (n = 105) and East Asian (n = 137) female university students completed questionnaires online. Caucasian women reported significantly higher levels of sexual desire, significantly lower levels of sexual conservatism, and significantly less sex guilt. In the entire sample, sexual conservatism and sex guilt separately mediated the relationship between ethnicity and sexual desire such that women with more sex guilt and those who were more sexually conservative reported lower sexual desire. Among the East Asian women, sex guilt, but not sexual conservatism, mediated the relationship between mainstream acculturation (degree of westernization) and sexual desire such that women with more sex guilt reported lower sexual desire. These findings suggest that sex guilt may be one mechanism by which ethnic groups differ in sexual desire.