This study examined the effectiveness of a professional development (PD) experience on preschool teachers' instructional strategy development. Focusing on supporting young children's peer social competence as a common interest, preschool teachers were guided to design the specific contents of the PD workshops and were offered an on-site facilitation opportunity, delineating teacher-driven and job-embedded approaches, respectively. Findings from this study suggest that teacher-driven PD workshops significantly increased teachers' perceived feasibility of implementing instructional strategies, and their actual use of those strategies was significantly influenced by job-embedded facilitations. In addition, preschool teachers considered physical classroom environment and children's language to be the most challenging factors in their instructional strategy implementation. Implications and directions for an effective PD model for preschool teachers are discussed. (Contains 6 tables.)