The aim was to examine anti-tumor necrosis factor α (anti-TNFα) therapy influence changes on Th17 and Th22 cells in patients with spondyloarthritis (SpA), and its correlation with changes in clinical and magnetic resonance imaging (MRI) activity and chronicity scores. The Th17 and Th22 cells were assessed at baseline, after 12 and 52 weeks of anti-TNFα therapy by flow cytometry (ClinicalTrials.gov NCT4682724). The percentages of both Th17 and Th22 cells were increased by 70% at baseline compared with healthy controls (both p < 0.01). During treatment, these two subsets increased further to be 170% (Th17) and 123% (Th22) above levels in healthy controls (both p < 0.01). The same subsets decrease their expression of IL-23R significantly during the observation period (p < 0.05). High levels of Th17 and Th22 cells at baseline were associated with the degree of chronic changes in the sacroiliac joints on MRI and a good clinical response to anti-TNFα treatment after one year. Plasma levels were not associated with clinical changes. Th17 cells, and Th22 subsets, increased during one year of anti-TNF-α therapy in SpA, regardless of their clinical improvement. This supports that both the Th17 and Th22 subsets could be involved in the progression in SpA.