This exploratory study examines the impact of a collaborative inquiry- and design-based afterschool program on urban high school students' IT/STEM learning--using information technology (IT) within the context of science, technology, engineering, and mathematics (STEM). The study used a mixed methods design, involving 77 participants within two cohort groups, each participating in an eighteen-month intervention period. Data were collected from the pre- and post-surveys, analysis of the participants' IT/STEM projects, external evaluation reports, and follow-up interviews. Findings indicate that the program had a significant impact on students' technology and IT/STEM skills, frequency of technology use, and understanding of IT use in STEM-oriented fields. Some degree of impact on attitude changes toward IT/STEM and career aspirations in these fields was also in evidence. The study demonstrates that IT/STEM experiences supported through technology-enhanced, inquiry- and design-based collaborative learning strategies have significant impact on urban high school students' IT/STEM learning. Effect of afterschool programs on attitude changes and IT/STEM-related career aspirations of urban high school students are recommended areas of further investigation.