Aim: of this study was to investigate the by-products acid whey and oat pomace as nutrient sources for succinic acid production by Actinobacillus succinogenes. Both by-products provide carbon sources in form of glucose and/or lactose without any pre-treatment. Yields of succinic acid per g total sugars consumed after 24 h were between 0.6 and 0.7 in control medium, acid whey, and in acid whey/oat pomace mixtures. A yield of more than 0.8 g per g was found in oat pomace after 24 h, which further increased to 1.0 g per g after 48 h. For the fermentation carried out with acid whey and oat pomace mixed at a ratio of 1:1 a productivity of 0.52 g L⁻¹ h⁻¹ was obtained. The productivities in control medium, acid whey, oat pomace, acid whey/oat pomace (2:1), and acid whey/oat pomace (3:1) were 16 %, 75 %, 48 %, 46 %, and 48 % less, respectively, indicating the necessity of finding the right balance of nutrients. The results of this study contribute to the decentralized utilization of food residues and even, despite the high value of succinic acid as platform chemical, to a recirculation into new food products.