Given the urgency of climate change, it is imperative to develop innovative technologies for repurposing CO₂ into value-added products to achieve carbon neutrality. Additionally, repurposing nitrogen-source-derived wastewater streams is crucial, focusing on sustainability rather than conventional nitrogen removal in wastewater treatment plants. In this context, microbial protein (MP) production presents a sustainable and promising approach for transforming recovered low-value resources into high-quality feed and food. We assessed MP production by hydrogen-oxidizing bacteria (HOB) utilizing CO₂ and various nitrogen sources. Specifically, we investigated MP production by two different HOB strains, Cupriavidus necator H16 and Xanthobacter viscosus 7d, within an integrated water-splitting biosynthetic system that generates in situ H₂ via water electrolysis. The electroautotrophically produced MPs of C. necator H16 and X. viscosus 7d exhibited amino acid contents of 555 and 717 mg protein/g cell dry weight, with 243 and 299 mg essential amino acid/g cell dry weight, respectively. They could serve as viable alternatives to conventional food/feed sources like fishmeal or soybean protein. Ammonium-rich wastewater streams are preferable for MP production in integrated bioelectrochemical systems. This study provides valuable insights into sustainable, carbon-neutral MP production using CO₂, water, renewable electricity, and recycled nitrogen sources.