The purpose of this study was to examine the degree to which high school students improved their inquiry capabilities in relation to scientific literacy through their experience of a problem-based environmental health science curriculum. The two inquiry capabilities studied were scientific questioning and approaches to inquiry into their own questions. A total of 129 high school students taught by two teachers in one school wrote responses to environmental health issues at the beginning and at the end of a 10-week long inquiry curriculum. An additional group of 46 students of one of the two teachers learned an alternative curriculum and participated as a comparison group. The students using the inquiry curriculum performed significantly better than those using the alternative curriculum in posing active inquiry questions and generating hypothesis-driven approaches to inquiry into their questions. The inquiry curriculum students also improved significantly from the pretest to the posttest in both measures of inquiry capacity. Among the students who were less prepared for inquiry in the beginning, 68% improved inquiry-questioning capability, while among the students who were more prepared for inquiry, 36% improved in generating hypotheses-driven approaches. Implications for curriculum design and implementation were provided along with further research suggestions.