: To analyze circulating immune cells in patients with anterior uveitis (AU) associated to axial spondyloarthritis (SpA), or juvenile idiopathic arthritis (JIA).: Venous blood samples were collected from healthy controls (n = 16), and either SpA (n = 19) or JIA (n = 23) patients with associated anterior uveitis (AU) during active flare, or after ≥3 months of inactivity. Frequencies of CD56, MHC-I, and S100A9 monocytes, CCR7 dendritic cells, CD56 natural killer (NK) cells and CD3CD56 T-cells were analyzed via flow cytometry. Serum S100A8/A9 levels were determined via ELISA.: SpA patients showed a reduced frequency of CD56 NK cells during uveitis activity, a constitutively activated monocyte phenotype, and elevated S100A8/A9 serum levels. In contrast, JIAU patients showed elevated frequencies of CD56 monocytes and CCR7 DC.: Phenotype of peripheral immune cells differ between patients, probably contributing to different courses of acute onset AU in SpA and insidious onset AU in JIAU patients.: AU: anterior uveitis, AR: arthritis, JIA: juvenile idiopathic arthritis, SpA: axial spondyloarthritis.