The aim of the present study was to assess the efficacy of feeding a higher-density formula (HDF) in infant with congenital heart disease (CHD).In a parallel randomized trial, infants (6 to 12 months) who underwent CHD corrective surgery received either a standard-density formula (SDF, 67 kcal /100 ml) or an HDF (90 kcal/100 ml) after discharge from the intensive care unit for 8 weeks. In addition to the formula, infants could receive breast milk or complementary food. Anthropometry, biochemistry, and formula intake were collected.Sixty-four infants completed the study (n = 32 in each group). All infants gained weight. The mean ± standard deviation (SD) of weight z score at baseline and week-8 were -2.38 ± 10.04 to -1.38 + 0.97 in the SDF group and -2.69 ± 1.19 to -0.89 ± 0.90 in the HDF group (between-group p = 0.0001). Both groups gained length, but showed a decline in length z-score which was significant in the SDF group but not significant in the HDF group. Mid-upper arm circumference and its z score improved in both groups, with more improvement in the HDF group. Serum albumin level was higher in the HDF than the SDF group at week-8, but no significant between-group differences were observed in hemoglobin, serum ferritin, or iron. Symptoms of gastrointestinal intolerance were not reported, but parents of 4 infants in the HDF group complained of their infants' constipation.Feeding infants using a concentrated formula could increase infants' weight gain and growth, and improve the nutritional status after CHD surgery.