A reversed-phase high-performance liquid chromatographic (HPLC) method is applied for the determination of galacturonic acid (GA) of pectins in different commercial fruit juices. The separation was carried out on a C18 column using precolumn derivatization with p-aminobenzoic acid (p-ABA) and UV detection at 304 nm. The identification of GA was confirmed by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) in positive ion mode. The concentration of GA in the samples analyzed ranged from 12.9 ± 0.5 to 49.4 ± 0.5 mgGA L−1. Amongst the samples analyzed, mango juice was found to be richest in GA content, and therefore a good source of pectins. Detection and quantification limits of the described methodology were 1.2 and 3.9 mg L−1, respectively. Quantitative GA recoveries in the beverages had a range between 90 and 98%. The results showed that the HPLC method proposed was precise and suitable for the identification and quantification of GA in commercial fruit juices.