Monodispersed Ni flower-like architectures with size of 1–2 μm were synthesized through a facile solvent-thermal process in 1,2-propanediol solution in the presence of polyethylene glycol (PEG) and sodium alkali for electromagnetic absorption application. The Ni architectures are composed of nanoflakes, which assemble to form three dimensional flower-like structure, and the thickness of nanoflakes is about 10–40 nm. A possible formation mechanism for Ni flower-like architectures was proposed and it was confirmed by the control experiments. The Ni architectures exhibited a saturation magnetization (Ms) of 47.7 emu/g and a large coercivity (Hcj) of 332.3 Oe. The epoxy resin composites with 20 vol% Ni sample provided good electromagnetic wave absorption performance (reflection loss <−20 dB) in the range of 2.8–6.3 GHz over absorber thickness of 2.6–5.0 mm.Graphical abstractMonodispersed Ni flower-like architectures composed of nanoflakes were synthesized through a facile solvent-thermal process. The Ni architectures exhibited a large coercivity and enhanced electromagnetic wave absorption in GHz.Highlights► Flower-like architectures composed of nanoflakes. ► A possible formation mechanism for Ni flower-like architectures was proposed. ► Sodium alkali, PEG, and NaCl played the important roles in the final morphology. ► Ni architectures exhibited a large coercivity (Hcj) of 332.3 Oe. ► Efficient electromagnetic absorption (RL<−20 dB) was provided in 2.8–6.3 GHz.