This study compared the aroma-active compounds in 14 brands of commercially available infant formula and investigated their changes during ambient storage after opening for 2 months. A total of 29 major aroma-active compounds were detected in infant formula. From the principal component analysis and heatmap analysis, a total of 14 brands of infant formula were classified into 3 groups. The second group contained JLB-Y, AY, and FH-F, of which 2-furanmethanol and (E,E)-3,5-octadien-2-one were the main compounds. The third group contained YL and JLB-L, with the characteristic flavor compounds in this group being mainly hexanal, heptanal, etc. Aldehydes, as the main volatile substances, account for more than half of the total volatiles. Nearly half of the aldehydes showed more significant changes after storage, e.g., hexanal, octanal, (E)-2-octenal, and 3-methylbutyraldehyde. The YL and YP-Q produced more saturated aldehydes after storage, being the concentration of hexanal in YL-2m and YP-Q-2m being 2 138.5 and 2 004.1 μg/kg, respectively. The concentrations of heptanal, octanal, and nonanal also increased relatively significantly, which may lead to a distinct rancid flavor in YL and YP-Q. Besides, among the ketones, (E,E)-3,5-octadien-2-one showed the greatest change after storage, especially in JLB-L. According to sensory evaluation experiments, the milky flavor of infant formulas decreased and fatty, rancid, fishy, and grassy flavors were found to have increased to different extents after storage. The current information gap on the concentration and evolution of volatile compounds in commercially available infant formula is filled by this study.