This study examined the relationship between response to intervention (RTI) implementation integrity in reading and student reading outcomes. Data were collected from 64 principals and school psychologists at 43 elementary schools. Hierarchical linear regression was used to examine the degree to which implementation of RTI tiers and key components predicted student reading assessment results, when controlling for a block of school demographic variables. Findings revealed that data-based decision making and Tier 3 implementation integrity significantly predicted student reading outcomes when controlling for significant demographic predictors. Interpretation of results and implications for research and practice are provided.