Black soybean cooking water (BSCW), a by-product of the soybean paste industry, is a novel foaming and emulsifying material. Its application, however, is limited to sauces and bakery goods. To expand its use, this research explored its binding and texturising abilities on a plant-based patty. This vegan patty was developed including methylcellulose (MC) at 3% or BSCW powder at 3, 6 and 12%, and their functional and textural characteristics were analysed. Adding BSCW powder at 12% resulted in enhanced fluid retention parameters, namely, decreased cooking loss (9.98 ± 0.72%; control: 12.64 ± 0.36%) and increased binding capacity (86.18 ± 0.47%; control: 83.26 ± 1.94%). Texturally, BSCW powder enhanced the hardness and adhesiveness of the patties. Consequently, BSCW powder could improve the characteristics of a minced-type vegan food similar to MC constituting an alternative plant-based ingredient that is environmentally friendly due to being sourced from an upcycled material.