The depolymerization of biolignin (BL), eucalyptus (EL), and hardwood lignins (HL) to simple aromatics was studied by a microwave assisted approach using NiO/H-ZSM-5 zeolites as catalysts. The catalysts prepared by the mechanochemical dry milling (MCDM) method contained bunsenite nano NiO particles with an average size of 67 μm at a concentration of 1–4.8 wt % NiO. Yields and composition of the obtained bio-oils are highly dependent on lignin type as well as on the content of NiO. The highest bio-oil yield (about 20 wt %) was obtained using 3.5 wt % NiO and HL as the feedstock. A number of relevant findings based depolymerization experiments are provided which pointed to different monomeric products (mostly S-derived) that could be produced in different proportions depending on the source of investigated lignin and content of the NiO at H-ZSM-5.