The isothermal section at 800°C and vertical sections of SmFe2–DyFe2 and (Sm0.86Dy0.14) Fex (1.6 ≤ x ≤ 2.4) in the Sm–Dy–Fe system were determined by using optical microscopy, X-ray diffraction analysis, electron probe microanalysis, and differential thermal analysis techniques. The isothermal section possesses 6 single-phase regions, 7 two-phase regions, and 3 three-phase regions. There are five intermetallic phases: (Sm, Dy) Fe2, (Sm, Dy) Fe3, (Sm, Dy)6Fe23, Th2Zn17-type (Sm, Dy)2Fe17, and Th2Ni17-type (Sm, Dy)2Fe17. No Sm6Fe23 and (Sm, Dy)2Fe7 phases exist in the ternary system. The vertical section of SmFe2–DyFe2 in the Sm–Dy–Fe system contains 2 single-phase regions, 2 two-phase regions, and 1 three-phase region. Investigation of the vertical section of (Sm0.86Dy0.14) Fex (1.6 ≤ x ≤ 2.4) indicates that it consists of 2 single-phase regions, 5 two-phase regions, and 1 three-phase region.