Background: Axial spondyloarthritis (axSpA) is a chronic inflammatory disease primarily affecting the axial skeleton causing pain, inflammation, and stiffness. Individuals with axSpA are at greater risk of developing cardiovascular disease, which can be counteracted by physical activity. High-intensity interval training (HIIT) has been shown to improve cardiovascular health, but the effect on disease activity and the level of inflammation in axSpA has been less studied. With the aim of investigating how levels of inflammatory cytokines, myokines, and protein markers for bone metabolism are acutely affected by one bout of HIIT, we studied serum from individuals with axSpA and healthy controls (HC). Methods: Ten participants with axSpA and 11 age- and sex-matched HC performed a single HIIT bout on a cycle ergometer: 4x4 minutes intervals with three minutes active rest in between. Blood samples were taken before and one hour after the HIIT bout. Serum proteins (IL-6, IL-17, IL-18, TNF, CXCL-10, VEGF-A, BDNF, DKK-1, osteoprotegerin, osteocalcin, osteopontin, BMP-7, CRP) were analyzed with a Luminex system or ELISA. A two-way ANOVA was used for comparisons. Results: A main effect from baseline to one hour post HIIT showed that both groups had a significant increase in serum levels of IL-6. VEGF-A was significantly lower in the axSpA group but was not affected by the HIIT bout. BMP-7 increased in both groups after the HIIT. For the other proteins analyzed, there were no significant differences in serum concentrations between individuals with axSpA and HC, or within the two groups before and after one bout of HIIT. Conclusions: One acute bout of HIIT significantly increases the serum concentrations of IL-6 and BMP-7 after one hour in both individuals with axSpA and HC, whereas serum levels of other proteins investigated are not changed.