This article summarizes the findings of research studies focusing on number sense instruction to improve mathematics competence of school going children. Twenty-three studies were located that met the inclusion criteria. Interventions gleaned from the review were categorized based on type of instruction (i.e., constructivist, explicit or a combination of the two). Treatment outcomes are discussed in relation to the various instructional approaches, student characteristics (e.g., grade, age), instructional features (e.g., materials, treatment length), assessment (formal, informal) and methodological features. Implications for classroom practice and future research directions are provided.