Background: Despite recent focus on patient safety in primary care, little attention has been paid to errors of omission, which represent significant gaps in care and threaten patient safety in primary care but are not well studied or categorized. The purpose of this study was to develop a typology of errors of omission from the perspectives of primary care providers (PCPs) and understand what factors within practices lead to or prevent these omissions.Methods: A qualitative descriptive design was used to collect data from 26 PCPs, both physicians and nurse practitioners, from the New York State through individual interviews. One researcher conducted all interviews, which were audiotaped, transcribed verbatim, and analyzed in ATLAS.ti, Berlin by 3 researchers using content analysis. They immersed themselves into data, read transcripts independently, and conducted inductive coding. The final codes were linked to each other to develop the typology of errors of omission and the themes. Data saturation was reached at the 26th interview.Results: PCPs reported that omitting patient teaching, patient followup, emotional support, and addressing mental health needs were the main categories of errors of omission. PCPs perceived that time constraints, unplanned patient visits and emergencies, and administrative burden led to these gaps in care. They emphasized that organizational support and infrastructure, effective teamwork and communication, and preparation for the patient encounter were important safeguards to prevent errors of omission within their practices.Discussion: Errors of omission are common in primary care and could threaten patient safety. Efforts to eliminate them should focus on strengthening organizational attributes of practices, improving teamwork and communication, and assigning manageable workload to PCPs.Conclusions: Practice and policy change is necessary to address gaps in care and prevent them before they result in patient harm. (J Am Board Fam Med 2017;30:733-742.)