AbstractWe report the synthesis of the novel heterometallic complex [Fe3Cr(L)2(dpm)6]⋅Et2O (Fe3CrPh) (Hdpm=dipivaloylmethane, H3L=2‐hydroxymethyl‐2‐phenylpropane‐1,3‐diol), obtained by replacing the central iron(III) atom by a chromium(III) ion in an Fe4 propeller‐like single‐molecule magnet (SMM). Structural and analytical data, high‐frequency EPR (HF‐EPR) and magnetic studies indicate that the compound is a solid solution of chromium‐centred Fe3Cr (S=6) and Fe4 (S=5) species in an 84:16 ratio. Although SMM behaviour is retained, the |D| parameter is considerably reduced as compared with the corresponding tetra‐iron(III) propeller (D=−0.179 vs. −0.418 cm−1), and results in a lower energy barrier for magnetisation reversal (Ueff/kB=7.0 vs. 15.6 K). The origin of magnetic anisotropy in Fe3CrPh has been fully elucidated by preparing its Cr‐ and Fe‐doped Ga4 analogues, which contain chromium(III) in the central position (c) and iron(III) in two magnetically distinct peripheral sites (p1 and p2). According to HF‐EPR spectra, the Cr and Fe dopants have hard‐axis anisotropies with Dc=0.470(5) cm−1, Ec=0.029(1) cm−1, Dp1=0.710(5) cm−1, Ep1=0.077(3) cm−1, Dp2=0.602(5) cm−1, and Ep2=0.101(3) cm−1. Inspection of projection coefficients shows that contributions from dipolar interactions and from the central chromium(III) ion cancel out almost exactly. As a consequence, the easy‐axis anisotropy of Fe3CrPh is entirely due to the peripheral, hard‐axis‐type iron(III) ions, the anisotropy tensors of which are necessarily orthogonal to the threefold molecular axis. A similar contribution from peripheral ions is expected to rule the magnetic anisotropy in the tetra‐iron(III) complexes currently under investigation in the field of molecular spintronics.