Increasing demand for animal protein has negative consequences on human health and the environment. Thus, the need for a replacement of animal protein with plant-based protein in the human diet is necessary. Therefore, the demand for selected plant-based protein (PBPs) (soybean, mushroom, potato, and cowpea) was assessed. Data collected from 343 staffers from the University of Ibadan were analysed using descriptive statistics and Quadratic Almost Ideal Demand System. Mushroom and soybean were luxury goods, but demand for mushrooms was more elastic than soybean. Potato was considered a necessary good. Expenditure elasticity for cowpea was, however, found to be just unitary. The selected plant-based proteins were normal goods. Furthermore, all the compensated own-price elasticities (except mushroom) were less than one (in absolute terms), indicating that they are price-inelastic. They ranged between (-0.14) for soybean and (-0.62) for potato. Hicksian elasticities showed that mushroom was a substitute for cowpea and potato. Cowpea and potato were also substitutes for each other. Socio-economic factors influencing demand were years of schooling, access to market, prices of the PBPs and marital status of the respondent.