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Antarctic krill (Euphausiacea superba) is an abundant and sustainable but underutilized natural resource with well-studied protein isolation methodology using Isoelectric solubilization-precipitation (ISP). The resulting krill protein isolate (KPI) has high yield and sufficient impurity removal in addition to desirable nutritional and functional properties but has yet to be used in food systems. Extrusion is a versatile and scalable food processing method with many benefits; thus, the aim of this study was to determine the impact of KPI as an additive in extrusion processing with the eventual goal of introducing it to human and animal food systems. KPI was isolated with standard ISP methodology and incorporated into four recipe formulations with moisture balanced control formulations. The moisture levels and dry ingredients for each formulation were 15% and 20% moisture 100% rice flour, 25% moisture pet food mix, and 33% moisture aquatic feed mix. Specific mechanical energy (SME), expansion, density, crushing force, and toughness were measured and the effects of altering isolate pH on KPI functionality was investigated for foaming, emulsion, and water retention properties. KPI elevated SME in rice flour blends but reduced SME in pet and aquatic feeds. In rice flour blends expansion and texture were largely unaffected. Pet food saw a decrease in radial expansion and an increase in density, and an increase in specific length with KPI addition. These changes did not significantly affect texture. Aquatic feed was significantly less dense and had slightly larger radial expansion with KPI addition and had reduced average crushing force, maximum crushing force, and toughness. KPI displayed better functionality when pH was altered compared to the isoelectric pH. Overall, KPI addition succeeded in this pilot study displaying strong potential for further research and use in food systems.