Chappell, Stephens, Kinnison, and Pettigrew (2009) conducted a study investigating educational diagnosticians knowledge of early reading development. Our study replicated the work of Chappell et al. through a mixed methods design that investigated educational diagnosticians’ perceptions and knowledge of early reading development. Additionally, our study sought to gain a better understanding of how educational diagnosticians selected assessment instruments. Our findings suggested that educational diagnosticians may lack understanding of the early developmental processes of reading and that there may be limited use of diagnostic assessment instruments when evaluating students who are struggling to read.