Formaldehyde (FA, CH2O) is one of the toxic volatile organic compounds that cause harmful effects on the human body. In this work, the interaction of FA gas with metal phthalocyanine (MPc) molecules was studied by employing density functional theory calculations. A variety of [MPc](a) (M = Sc, Ti, and V; a = -1, 0, and +1) complexes were studied, and the electronic properties, interaction energies, and charge transfer properties of all of the studied molecules were systematically discussed. Among the studied complexes, the Sc and Ti phthalocyanines were more reactive toward the adsorption of FA gas. Moreover, it was revealed that the interaction of the [ScPc](+1) and [TiPc](0) complexes with the CH2O molecule was stronger,, in which the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy gap of 46% and 36% decreased after FA adsorption. The results indicated that the MPc-based materials may be a promising candidate for the detection of FA gas.