Natural killer (NK) cells express abundant levels of killer-specific secretory protein of 37 kDa (Ksp37), an unexplored molecule only expressed by NK and T cells. Ksp37, encoded by FGFBP2, is the least characterized member of the fibroblast growth factor binding protein (FGFBP) family. FGFBPs are co-factors that bind fibroblast growth factor 1 (FGF1) and FGF2 to facilitate downstream signaling via FGF receptors (FGFRs). Structurally, Ksp37 has a predicted FGF2 binding domain, but its function remains unknown. Here we have characterized Ksp37 expression in primary NK cells using RNAseq and flow cytometry to identify increased expression in line with differentiation. Mature CD56^dim NK cells exhibit a unique localization pattern of Ksp37 (polarized) compared to immature CD56^bright NK cells (diffuse). Ksp37 is rapidly secreted in a dose-dependent and JAK1-dependent manner upon cytokine stimulation followed by rapid reloading post-stimulation. In NK-92 cells, Ksp37 secretion was facilitated by Rab19⁺ late endosomes and Rab8a⁺ exocytic vesicles. CRISPR/Cas9-mediated knockout of FGFBP2 did not impact NK cell functionality (degranulation, killing) nor phenotype, hinting at Ksp37 likely playing a role outside of the cell. Lastly, in line with its predicted FGF2 binding domain, we have confirmed Ksp37-FGF2 binding. Here, we characterized Ksp37 expression in rested and stimulated NK cell subsets and delineated its secretory pathway. Binding of released Ksp37 to FGF2 could influence FGF2 abundance and FGFR signaling, which may have important implications for tumor growth, metastasis, angiogenesis, tissue repair and pregnancy.