This study investigates the development of plural adjective agreement in Hebrew, focusing on the consolidation of Hebrew number/gender morphology in children and adolescents across the school years in comparison with adults. A total of 240 Hebrew-speaking participants in seven consecutive grade levels (kindergarten to sixth grade) plus a group of 30 adults were administered a set of 32 singular noun-adjective noun phrases, which they had to pluralize. Head nouns were classified by noun gender (masculine and feminine), suffix type (regular and irregular), and stem type (nonchanging and changing). Children's ability to correctly pluralize nouns and adjectives increased markedly from kindergarten to adulthood, whereas reaction time to the correct plural phrase decreased concomitantly. Noun gender, stem, and suffix morphology impacted noun and adjective plural marking as well as reaction time. Results are discussed in view of the critical role of noun gender as a central organizing factor in the development of Hebrew plural marking.