Three-dimensional flower-like Ni(NiO) decorated on two-dimensional Ti3C2Tx/TiO2 composites were successfully synthesized by an in situ solvothermal reaction, and the electromagnetic (EM) wave absorption performance of the hybrids were explored at 2.00–18.00 GHz. The as-prepared Ni(NiO)/Ti3C2Tx/TiO2 composites include flower-like Ni(NiO) with uniform distribution on the surface of Ti3C2Tx MXenes and part of them get into the space between interlayers. The Ni(NiO)/Ti3C2Tx/TiO2 composites exhibit a maximum reflection loss (RL) value of −41.74 dB at 14.96 GHz with the absorber thickness of merely 1.3 mm and the effective absorption bandwidth (EAB) reaches 3.20 GHz. The outstanding electromagnetic wave absorbing performance can be attributed to the dielectric loss of Ti3C2Tx MXenes and multi-phase heterostructures, the magnetic loss of Ni(NiO) and their synergistic loss mechanism. Moreover, the zigzag path formed by flower-like Ni(NiO) also has a great consumption effect on electromagnetic waves by incurring the eddy current under the affect of alternating EM waves. The laminated structure of Ti3C2Tx MXenes also dissipates microwaves by offering the space for multiple reflections and scattering. This paper furnished a novel modus for synthesizing original EM wave absorption materials and making the balance among thickness, broad bandwidth, oxidation resistance and light weight, which makes Ni(NiO)/Ti3C2Tx/TiO2 composites a hopeful material for microwave absorption (MA).