The endocrine fibroblast growth factor 21 (FGF21) requires both fibroblast growth factor receptor (FGFR) and β‐Klotho for signaling. In this study, we sought to understand the inter‐molecular physical interactions in the FGF21/FGFR/β‐Klotho complex by deleting key regions in FGFR1c or FGF21. Deletion of the D1 and the D1‐D2 linker (the D1/linker region) from FGFR1c led to β‐Klotho‐independent receptor activation by FGF21, suggesting that there may be a direct interaction between FGF21 and the D1/linker region‐deficient FGFR1c. Consistent with this, the extracellular portion of FGFR1c lacking the D1/linker region blocked FGF21 action in a reporter assay, presumably by binding to and sequestering FGF21 from acting on cell surface receptor complex. In addition, the D1/linker region‐deficient FGFR1c had enhanced interaction with β‐Klotho. Further, we demonstrated that deletion of the D1/linker region enhanced the formation of the FGF21/β‐Klotho/FGFR1c ternary complex in both Biacore and asymmetrical flow field flow fractionation studies. Finally, we found that the N‐terminus of FGF21 is involved in the interaction with FGFR1c and FGF21/β‐Klotho/FGFR1c ternary complex formation. Taken together, our data suggest that the D1/linker region regulates both the FGF21/FGFR1c and FGFR1c/β‐Klotho interaction, and a direct interaction of FGF21 with FGFR1c may be an important step in receptor‐mediated FGF21 signaling.