Increasing consumer awareness of health and climate is being reflected in their dietary choices. This is reflected in the strong growth in the market for plant-based food, with plant-based burgers (PBB) being the most popular meat alternative. PBB must be based on natural ingredients that increase nutritional value, improve technological properties, and create satisfying physical sensations. Fibers obtained from agri-food by-products can potentially meet all of these requirements. The dietary fiber concentrate (DFC) produced from the forced roots of Belgian endive (Cichorium intybus var. foliosum) (by-product) has shown potential for application in PBB. Replacing soy protein with 5% and 10% of DFC from Belgian endive (DFC-BE) resulted in lower caloric value and sugar content and doubled dietary fiber concentration in the end product, enough to justify a “high fiber” nutrition claim (>6 g per 100 g). Baking properties such as baking yield, moisture retention, and dimeter reduction also improved. Application of DFC-BE can also be used to regulate pH, color, texture profile, and sensory attributes. Individual recipes must be adjusted to obtain the required results.