Decades of research studies suggest that the quality of parenting skills and parenting knowledge about children’s development have profound effects on children’s development. Studies to date show that most adults lack knowledge of child development and developmentally-appropriate child guidance. These studies, however have focused on white, middle-class, well-educated women and are limited in the range of issues addressed. The purpose of this study was to gain a more accurate understanding about adults’ knowledge of child development and child guidance by assessing female and male adults using an ethnically diverse population. Data from 705 adult participants showed that adults knew more than expected about child development, but lacked knowledge about developmentally-appropriate child guidance. Knowledge also varied by the amount of child development coursework taken. Results also showed that females were more knowledgeable than males, and knowledge varied somewhat by ethnicity with European-Americans being more knowledgeable in both child development and child guidance than other ethnic groups. These findings suggest that more work needs to be done to disseminate research- and evidence-based findings about child development and child guidance as the implications of this knowledge for child well-being are profound. The results of this study help to inform the design and content of parent education classes and related interventions to address gaps in knowledge and skills.