The purpose of this meta-analysis was to examine the effectiveness of early numeracy interventions for young students, including students with disabilities or those at-risk for mathematics difficulty (MD). This study evaluated preschool, kindergarten, and first-grade interventions on early numeracy content, instructional features, and methodological components that improved students' mathematics achievement. A total of 33 studies met inclusion criteria for this meta-analysis, with 51 treatment groups. Excluding outliers, the average weighted effect size for numeracy interventions across 49 treatment groups was moderate (g = 0.63), and the 95% confidence interval did not include zero [0.50, 0.73]. Results indicated that early numeracy interventions that included preschool and kindergarten students produced larger treatment effects than interventions with first-grade participants; in addition, treatment effects were slightly higher on average for students identified as at-risk for MD according to low socio-economic status and performance greater than the 25th percentile on a mathematics screener, compared to students who were identified as typically achieving or at-risk for MD according to performance below the 25th percentile. The results of the final meta-regression model for the total sample of studies indicated that the following predictors accounted for the most between-studies variance: concrete-representational-abstract instructional framework, intervention duration, risk status of participants, and the inclusion of counting with one-to-one correspondence in the intervention content (Pseudo R[superscript 2] = 75%). Directions for future research on conducting interventions are provided, and implications for educators implementing early numeracy interventions are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]