Findings from three field-tests of parents’ ratings of early childhood intervention practice guides are reported. Results from the first field-test were used to inform changes to the practice guides in the second field-test, and results from the second field-test were used to inform changes to the practice guides in the third field-test. Parents’ judgments of the practice guide designs and their social validity appraisals of the practice guide intervention activities and child outcomes were correlated with parent-informed improvements in the intervention materials. The results add to the knowledge base in terms of how parent-informed improvements to the practice guides are related to product design judgments and the social validity appraisals of the importance and acceptability of early childhood intervention materials.