This work reports the growth of magnesium oxide (MgO) nanocubes by thermal chemical vapor deposition at various temperatures. The MgO nanocubes were investigated by X-ray diffraction, FESEM, EDAX, TEM and FTIR studies to study its various properties. The material is well-dispersed and has a cubical shape with an average size of 16 nm. XRD shows a face cubic centered structure, and SEM and TEM reveal nanocube morphology. The mechanism of the growth process is briefly detailed. The MgO nanocubes, if deposited on an overhead projector sheet, can be used as a chemoresistive sensor for hydrogen at a constant temperature of typically 200 °C and an applied voltage of 5 V. The sensor can detect hydrogen in the 3000 to 5000 ppm concentration range, and the lowest detectable concentration (at a signal-to-noise ratio of 3) is 3000 ppm. [Figure not available: see fulltext.]. © 2017, Springer-Verlag Wien.