This study examined infant and young child feeding (IYCF) counseling, decision-making, and practices among HIV-infected women with children 0–23 months participating in Malawi’s Option B+ prevention of mother-to-child transmission (PMTCT) program. We conducted 160 survey interviews, 32 in-depth interviews, and 32 observations of PMTCT visits. Surveys indicated that exclusive breastfeeding was common (75 %) among children <6 months, while minimum dietary diversity (41 %) and minimum acceptable diet (40 %) for children 6–23 months occurred less often. In-depth interviews supported these findings. Most women felt comfortable with current breastfeeding recommendations, but chronic food insecurity made it difficult for them to follow complementary feeding guidelines. Women trusted IYCF advice from health workers, but mainly received it during pregnancy. During observations of postnatal PMTCT visits, health workers infrequently advised on breastfeeding (41 % of visits) or complementary feeding (29 % of visits). This represents a missed opportunity for health workers to support optimal IYCF practices within Option B+.