This article discusses how increasing diversity within a community requires health care professionals to reassess the developmental assessment tools being used, or at the least, what implications one can derive from resultant identification of delays. The author describes a culture clash between her training and developmental expectations as a physical therapist practicing in the San Francisco Bay Area and the upbringing and cultural expectations of a recently immigrated young Guatemalan Maya Mam mother and her medically fragile infant. The author explores the concepts of cultural humility and mentalization as strategies to aid in development of a therapeutic relationship when working with families from diverse cultural backgrounds.