Sugar beet molasses is one of the most important by-products of the sugar industry. The present study investigates the optimization of microwave-assisted (MAE) and ultrasound-assisted (UAE) extraction conditions of sugar beet molasses powder in terms of total phenolic content (TPC), total flavonoid content (TFC), free radical scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP). A three factor, and three level Box–Behnken design was used to optimize microwave power, extraction time, and methanol concentration conditions for MAE and ultrasound amplitude, extraction time, and methanol concentration for UAE. The optimal MAE parameters were a microwave power of 420 W, an extraction time of 70 s, and a methanol concentration of 30%. For UAE, an amplitude level of 90%, an extraction time of 300 s, and a methanol concentration of 46% were determined as optimal conditions. Novelty impact statement: Sugar beet molasses is one of the most important by-products of sugar production. Giving the molasses in powder form is practical in many ways, for example, in use, storage, and sampling. There is no other study in which ultrasound and microwave-assisted extraction using RSM has been optimized to extract bioactive components from sugar beet molasses powder. This study demonstrated that microwave-assisted extraction is a more effective method for extracting bioactive compounds from sugar beet molasses powder than ultrasound-assisted extraction.