Enrollment and completion rates at the Upper Secondary Education (USE) level are the lowest of any tier in the Mexican education system. One of the policies intended to address this issue is the conditional cash transfer program Oportunidades, which targets the country’s most disadvantaged households and provides higher subsidies for girls than for boys. Impact evaluations of the program have proven its effectiveness in primary and lower secondary education. However, its effect on USE completion has not been analyzed and little is known about the gender heterogeneity effects at this level of schooling. Using a Difference-in- Difference analysis, I find that Oportunidades has a negative effect on boys’ USE completion and no effect on girls. This evidence suggests that redesigning the program is necessary in order to improve its effectiveness on USE outcomes.