To create a gluten-free flour that closely mimic wheat in terms of its physico-chemical characteristics, a careful combination of several replacements is necessary. Therefore, the goal of this study was to develop a composite flour devoid of gluten using rice (R), Cardaba banana (C), and pigeon pea (P) and to evaluate its techno-functional qualities. Using 12-runs optimal mixture experimental design, 5 composite blends containing varying percentage of rice, Cardaba banana and pigeon pea flours were chosen based on dietary fiber. The blends containing 22% pigeon pea and above exhibited significantly higher protein (7.59–8.36 g/100 g), fiber (2.39–3.05 g/100 g), ash (1.94–2.34 g/100 g), total phenols (6.49–6.78 mg gallic acid equivalent/g), flavonoids (0.03–0.04 mg quercetin equivalent/g), and antioxidant properties in terms of ferric reducing antioxidant power, Fe2+-chelating capacity and ·OH scavenging abilities. However, these flour blends, due to the large proportion of pigeon pea retained higher but tolerable level of some antinutritional factors such as phytate (4.53–7.00 mg/100 g), tannin (0.30–0.44 mg/g), and trypsin-inhibitor (8.69–10.49 mg/100 g). Conversely, dietary fiber (both soluble and insoluble), resistant starch, amylose, amylopectin, and essential micronutrients including Na, Ca, and Zn were the main features of R79-C06-P15 composite blend. A biplots in the context of principal component analysis model with 78% explained variance (R2 = 0.78), graphically revealed the distinctive nutritional and functional attributes of each of the flour blend. Therefore, depending on the intended application, blends of rice, Cardaba banana, and pigeon pea flour at various percentages may result in a gluten-free flour with a range of nutritional and techno-functional properties.