Many scholars have argued that an intercultural approach to foreign language instruction best reflects the inherent interconnectedness of language and culture. However, abundant evidence of the effectiveness of such an approach is lacking, particularly at the secondary level. This two-year curricular experiment, which took place in two public high schools in the United States, investigated the impact of explicit instruction in intercultural communication theories and direct participation in activities designed to promote intercultural competency on the attitudes and motivation of secondary learners of Spanish as a foreign language. Data for both the experimental and control groups showed that students' pretest attitudes toward the Spanish language and Spanish-speaking cultures were generally positive. Comparisons of pre- and posttest scores showed that the treatment group showed a statistically significant increase in positive attitudes, including increases in both integrative and instrumental motivation, as well as more positive attitudes toward both European Spanish speakers and U.S. Hispanics. Results showed that, for one control group, students' attitudes did not change, and attitudes of students in the second control group became less positive over the period under consideration.