Guidelines recommend closer outpatient follow-up for exclusively breastfed newborns, especially those with pronounced weight loss, because of increased risk of hyperbilirubinemia and dehydration that might require readmission. Our objective was to determine how feeding method and weight loss are associated with neonatal health care utilization. A retrospective cohort study conducted at Northern California Kaiser Permanente hospitals in 2009-2013 assessed 143,889 neonates to study the inpatient method of feeding as well as inpatient and outpatient weights. The main outcome measures were inpatient and outpatient health care utilization in the 30 days after birth. Newborn weight loss and feeding method were both associated with utilization. Exclusively breastfed newborns had higher readmission rates than those exclusively formula fed for both vaginal (4.3% compared to 2.1%) (P < .001) and cesarean deliveries (2.1% compared to 1.5%) (P = .025). Those exclusively breastfed also had more neonatal outpatient visits compared to those exclusively formula fed for both vaginal (means of 3.0 and 2.3, P < .001) and cesarean deliveries (means of 2.8 and 2.2, P < .001). Among vaginally delivered newborns of all feeding types, newborns with weight loss >10% at discharge had a relative risk of readmission of 1.10 (95% confidence interval [CI],1.00, 1.20) compared to those with <8% weight loss at discharge; among the subset weighed as inpatients or outpatients between 48 and 72 hours, those with >10% weight loss between 48-72 hours had a relative risk of readmission of 2.11 (95% CI, 1.95, 2.26) compared to those with <8% weight loss at 48-72 hours. Exclusive breastfeeding and weight loss are associated with increased neonatal health care utilization. Improving clinical management of exclusively breastfed neonates with pronounced weight loss might reduce health care utilization.