Objective: It is in order to examine associations between social desirability (SD) and self-reports of abstinence among youths in rural Ethiopia. Methods: Youths of ages 15-24 (114 participants) were administered questionnaire to assess HIV knowledge and primary abstinence and a modified Marlowe-Crowne Social Desirability Scale to assess SD bias. The relationships between SD groups (dichotomized into high and low) and abstinence by various characteristics were assessed by using Fisher’s exact p-values. Results: The odds of individuals reporting abstinence were 13.2 times greater in the high SD group compared to the low SD group (p-value 0.002) when adjusted for education, gender, age group, and HIV knowledge. The differences in abstinence between the high and low SD score groups were also examined for selected variables. Conclusions: Individuals who exhibited more SD bias were more likely to report primary abstinence. SD bias should be considered when conducting self-reported surveys to measure the effectiveness of HIV prevention programs.