The textile industry has been exploring sustainable chemicals and natural alternatives to replace harmful and carcinogenic substances used in different stages of textile production for dyeing textiles. Natural dyes are gaining popularity, as they are environmentally friendly and less harmful. Betacyanin, a type of pigment obtained from red pitahaya, commonly known as red dragon fruit (Hylocereus polyrhizus), has peels that are available as agricultural waste and can be used to meet the demand for natural dye production. This study aimed to explore and utilize dragon fruit’s peel as a natural colorant for dyeing 100% cotton knit fabric (scoured and bleached single jersey plain knit) of 170 g/m², which could transform a low-value material into a valuable product. However, cotton’s phenolic nature and oxidation process result in negative charges on its surface, making natural dyeing challenging. Cationization with cationic agents (ForCat NCH, a mixture of cationic polyamine and 1,3,dichlori-2-propanol) and mordanting (potassium alum or potassium aluminum sulfate) were carried to improve dye exhaustion and enhance colorfastness properties. Spectrophotometer 800 was used to measure color strength (K/S), and several fastness tests, including wash, perspiration, and rubbing were conducted to assess the final product’s performance. The process parameters, such as temperatures, times, pH levels, and dye concentrations were varied to understand better the optimum conditions.