Growing a national certification program requires systematic research to determine its impact on certificate holders and effectiveness in serving the public. Launched in 2007, the literature to date on the efficacy and value-added effect of the Nationally Certified Educational Diagnostician (NCED) credential is virtually nonexistent. Increased awareness of the educational diagnostician profession coupled with heightened job prospects, however, warrants the need for research on the NCED. The purpose of this study was to investigate whether professional practices of educational diagnosticians holding national certification differed significantly from those without national certification. Researchers administered a 24-item questionnaire to 262 educational diagnosticians which elicited self-ratings of six domains of professional practices. Analysis of variance results showed that NCED holders had significantly higher mean self-ratings than their non-NCED counterparts in the areas of leadership/policy and collaboration. Acknowledging NCED's value-added potential, researchers offer explanations for these findings in light of related research on other national credentials, as well as limitations to the study and implications for future research.