In the quest for 2D conducting materials with high ferromagnetic ordering temperature the new family of the layered Fe_nGeTe₂ compounds, especially the near-room-temperature ferromagnet Fe₄GeTe₂, receives a significant attention. Fe₄GeTe₂ features a peculiar spin reorientation transition at T_SR ≈ 110 K suggesting a non-trivial temperature evolution of the magnetic anisotropy (MA)—one of the main contributors to the stabilization of the magnetic order in the low-dimensional systems. An electron spin resonance (ESR) spectroscopic study reported here provides quantitative insights into the unusual magnetic anisotropy of Fe₄GeTe₂. At high temperatures the total MA is mostly given by the demagnetization effect with a small contribution of the counteracting intrinsic magnetic anisotropy of an easy-axis type, whose growth below a characteristic temperature T_shape ≈ 150 K renders the sample seemingly isotropic at T_SR. Below one further temperature T_d ≈ 50 K the intrinsic MA becomes even more complex. Importantly, all the characteristic temperatures found in the ESR experiment match those observed in transport measurements, suggesting an inherent coupling between magnetic and electronic degrees of freedom in Fe₄GeTe₂. This finding together with the observed signatures of the intrinsic two-dimensionality should facilitate optimization routes for the use of Fe₄GeTe₂ in the magneto-electronic devices, potentially even in the monolayer limit.