Engaging youth in citizen science projects has multiple benefits. Yet, numerous challenges, such as lack of alignment between project goal and youth interest, hinder youth wider engagement. In this paper, we suggest a model for engaging volunteers in facilitator roles, warranting positive outcomes for youth engagement in citizen science projects. Grounded in a community of practice approach, our model involves facilitators, with experience in youth engagement, as co-designers from project onset. The facilitators' engagement in the co-design process triggers rich interactions among project designers, enables the facilitators to leverage their expertise in shaping and refining the project, and ensures its youth-centric design. To demonstrate the utility and contribution of our model, we present a case study of 13 nature youth counselors from a nature protection organization, engaged as facilitators in a biodiversity citizen science project. Our paper offers a new perspective on facilitators' roles and contribution to citizen science initiatives. It provides a model for facilitator engagement in a youth-centric citizen science initiative, reveals ways in which facilitators enrich the design and sustainability of the project, and calls for wider adaptation of such a role for the engagement of youth within the citizen science landscape.