OBJECTIVE Disparities persist in breastfeeding exclusivity and duration despite increases in breastfeeding initiation. The objective of this study was to examine factors that influence maternal decision making surrounding infant feeding practices over time in a diverse inner-city population. METHODS We conducted a prospective qualitative study with 20 mothers recruited from 2 urban primary care clinics. Participants completed open-ended interviews and demographic questionnaires in English or Spanish administered at approximately 2 weeks and 6 months postpartum. Transcripts were analyzed using a combined technique of inductive (data-driven) and deductive (theory-driven, based on the Theory of Planned Behavior) thematic analysis using 3 independent coders and iterative discussion to reach consensus. RESULTS All women initiated breastfeeding, and 65% reported perceived insufficient milk (PIM). An association between PIM and behavioral control emerged as the overarching theme impacting early breastfeeding cessation and evolved over time. Early postpartum, PIM evoked maternal distress-strong emotional responses to infant crying and need to control infant behaviors. Later, mothers accepted a perceived lack of control over milk supply with minimal distress or as a natural process. Decisions to stop breastfeeding occurred through an iterative process, informed by trials of various strategies and observations of subsequent changes in infant behavior, strongly influenced by competing psychosocial demands. CONCLUSIONS Infant feeding decisions evolve over time and are influenced by perceptions of control over infant behavior and milk supply. Tailored anticipatory guidance is needed to provide time-sensitive strategies to cope with challenging infant behaviors and promote maternal agency over breastfeeding in low-income populations.