This mixed-methods study examined influences, factors, and processes associated with parental recognition and appraisal of developmental concerns among 23 English- and Spanish-speaking parents of young children with signs of developmental or behavioral problems. Participants shared their experiences through in-depth interviews or focus groups and also completed questionnaires assessing children's developmental status and parental knowledge of infant and child development and other demographics. Half of the participants reported behavior, social, or speech concerns; more than a third had academic, receptive language, or self-help concerns; and roughly 15% reported fine or gross motor concerns. Although parent knowledge of child development was low (average 50%-65% correct), level of concern was consistent with referral for services. Parents clearly engaged in a sophisticated process of observing their children over time and across settings, comparing the index child with peers or to siblings when they were of the same age. In addition, parents considered the child's temperament, health status, and environment as part of the appraisal process. These findings suggest that parents and caregivers of young children may benefit from shared knowledge and information about typical and atypical child development behaviors and that their concerns should be considered as sophisticated responses indicating the need for referral.