Parental concerns are useful tools to help pediatric care providers identify the presence of developmental and behavioral problems. This study sought to learn whether specific parental concerns helped predict diagnoses in a tertiary developmental clinic. Parents of preschoolers who attended a preschool developmental clinic (n = 101) were surveyed about behavioral and developmental concerns and their concerns about possible diagnoses. Clinical diagnoses were subsequently obtained on all children and compared with parents’ primary concerns. In our sample, approximately 50% of concerns were about language development and 21% about behavior. The most common diagnoses were communication disorder (41%) and developmental delay (42%). Only 30% of children whose parents had concerns about an autism spectrum diagnosis had actually received that diagnosis. Neither parental concerns about development and behavior nor their concerns about specific diagnosis predict clinical diagnosis in our tertiary developmental setting.