A simple and fast method has been developed and validated for the determination of myo-inositol in milk powder samples, using solid-liquid extraction with water (0.01% formic acid, v/v):methanol (1:1, v/v). The determination was carried out by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) using an electrospray ionisation source (ESI) in positive mode. Chromatographic separation was carried out using as mobile phase water (0.01% formic acid, v/v) and methanol in gradient mode. Data acquisition under MS/MS was achieved by applying selected reaction monitoring, using 181.0→109.0 and 181.0→81.0 for quantification and confirmation purposes, respectively. The technique provides a sensitive and selective determination of myo-inositol in the analysed samples, with a run time of 4min. The limit of detection and quantification were 0.2 and 0.5mgkg(-1), respectively. The method was applied to six fortified commercial milk powder samples containing myo-inositol amounts ranging from 290 to 2200mgkg(-1).