Counting is foundational to success with mathematics. In this synthesis, we analyzed 17 studies about counting-focused interventions for preschool and kindergarten students with mathematics difficulty or at-risk of mathematics difficulty. All interventions addressed several components of counting, including stable order, one-to-one correspondence, and cardinality. After students participated in a counting-focused intervention, results indicated moderate-to-strong proximal effects and positive transfer effects. Computer game-based counting interventions without instructional strategies had no significant effects on preschool students. Modeling, guided practice, feedback, and multiple representations (i.e., hands-on or virtual) were the most common instructional strategies used within the interventions.