Identification of autism spectrum disorder (ASD) has been occurring at earlier ages, leading to a need for interventions that suit this age range. Because young children's development is highly dependent on adults and positive adult relationships, fields that traditionally have success in treating ASD, such as Applied Behavior Analysis (ABA), must explicitly consider relationships. At the same time, Infant/Early Childhood Mental Health (I/ECMH) specialists that have traditionally focused on the parent and child relationship must recognize the importance of addressing atypical or difficult child behavior as major motivating factor or port of entry with families. This paper discusses two seemingly different approaches to the treatment of young children, the Applied Behavior Analysis (ABA) informed Early Start Denver Model (ESDM) and Infant/Early Childhood Mental Health (I/ECMH) and proposes that they are complementary therapies that can be used simultaneously within the context of an interdisciplinary team to treat the "whole" child and his/her relationships. As demonstrated by the case example, combining the strengths of ABA and mental health services when working with very young children and families has the potential for many benefits.