Aims: The effect of race/ethnicity on the risk of obesity associated with short or long sleep durations is largely unknown. This study assessed whether the sleep–obesity link differentially affects black and whites. Methods: Analysis was based on data obtained from 29,818 adult American respondents from the 2005 National Health Interview Survey, a cross-sectional household interview survey. Results: Multivariate-adjusted odds ratios for obesity associated with short sleep (≤6 h) among blacks and whites were 1.98 (95% CI: 1.69–2.30) and 1.20 (95% CI: 1.10–1.31), respectively, and with long sleep (≥9 h) for blacks and whites were 1.48 (95% CI: 1.14–1.93) and 0.77 (95% CI: 0.67–0.89), respectively (all p < 0.001). Conclusion: Race/ethnicity may have significantly influenced the likelihood of reporting obesity associated with short and long sleep durations. Relative to white respondents, an excess of 78% of black respondents showed increased obesity odds associated with short sleep. Black long sleepers also showed increased odds for obesity, but white long sleepers may be at a reduced obesity risk.