To look closely at definitions of competency for those who specialize in infant mental health (IMH), the authors conducted a careful examination of interviews with IMH home visitors. The interview responses were categorized and then compared with interviews with the families who were served by the same IMH home visitors and with competency definitions previously established by professional organizations and leaders in the field. These comparisons identified themes in the areas of knowledge, skill, and reflective practice that can inform the development of education and training to better prepare and support practitioners who choose to specialize in IMH. The identified key training categories are infant-toddler development, observation skills, family studies, infant and parent mental health, relationships, and reflective practice.