Four biradical‐Ln complexes with different transition metal ions, namely [LnM(hfac)5(NITPh‐PyPzbis)] (MII=MnII and LnIII=Gd 1, Dy 2; MII=NiII and LnIII=Tb 3, Dy 4), were prepared by the reaction of Ln(hfac)3 ⋅ 2H2O, Mn(hfac)2 ⋅ 2H2O or Ni(hfac)2 ⋅ 2H2O with NITPh‐PyPzbis biradical (hfac=hexafluoroacetylacetonate, NITPh‐PyPzbis=5‐(3‐(2‐pyridinyl)‐1H‐pyrazol‐1‐yl)‐1,3‐bis(1'‐oxyl‐3'‐oxido‐ 4',4',5',5'‐tetramethyl‐4,5‐hydro‐1H‐imidazol‐2‐yl)benzene). In complexes 1–4, the NITPh‐PyPzbis biradical chelates one LnIII ion by means of its aminoxyl moieties and the transition metal ion is introduced through the two N donors from the pyridyl pyrazolyl moiety. Magnetic investigations indicate that complex 4 displays visible maxima in frequency/temperature‐dependent χ′′ signals with two‐step relaxation processes, but complex 2 exhibits no slow magnetization relaxation. The comparison of structure parameters of both Dy complexes indicates that the symmetries of coordination spheres of two Dy ions are D2d for 2 and C2v for 4, which thus probably results in different magnetic relaxation behaviors. This work provides new insight for improving properties of Ln‐biradical based SMMs. [ABSTRACT FROM AUTHOR]