INTRODUCTION: Kazakhstan has one of the fastest-growing HIV epidemics in the world, with increasing rates among adolescents and young adults (AYA). Innovative strategies are needed to increase HIV testing uptake and decrease HIV stigma among AYA. Citizen science, defined as the active engagement of the general public in scientific research tasks, promotes and facilitates community engagement throughout the research process. This citizen science study used crowdsourcing to engage AYA in Kazakhstan to develop a digital intervention to reduce HIV stigma and promote HIV self-testing. Our objectives in this paper are to describe the approach used, its feasibility and acceptability, and AYA motivations for and lessons learned collaborating on the study. METHODS: From October 2021 to July 2022, in collaboration with a Community Collaborative Research Board and a Youth Advisory Board, we developed an open call requesting multimedia submissions to reduce HIV testing stigma. Eligible submissions were separated by age group (13-19 or 20-29 years) and judged by a panel composed of AYA (n = 23), healthcare professionals (n = 12), and representatives from the local government and non-governmental organizations (n = 17). Each entry was reviewed by at least four judges and ranked on a 5-point scale. The top 20 open call contestants were asked to submit self-recordings sharing their motivation for and experience participating in the contest and lessons learned. Descriptive statistics were calculated for quantitative data. Qualitative data were coded using open coding. RESULTS: We received 96 submissions from 77 youth across Kazakhstan. Roughly, three-quarters (n = 75/96) of entries met judging eligibility criteria. Of the eligible entries, over half (n = 39/75) scored 3.5 or higher on a 5-point scale (70.0%). The most frequent types of entries were video (n = 36/96, 37.5%), image (n = 28/96, 29.2%) and text (n = 24/96, 25.0%). AYA's primary motivations for collaborating on the study included a desire to improve society and help youth. The main challenges included creating content to address complex information using simple language, finding reliable information online and technological limitations. CONCLUSIONS: Crowdsourcing was feasible and highly acceptable among AYA in Kazakhstan. Citizen science approaches hold great promise for addressing the increasingly complex health and social challenges facing communities today.