This work reports the synthesis of polyvinylbutyral (PVB)-MnO2 nanocomposites and their microwave absorption property. Anisotropic nanoparticles loaded polymer nanocomposites have better dielectric properties. Therefore, to investigate the morphology controlled microwave absorption property, MnO2 nanorods and MnO2 nanospheres were synthesized by low temperature chemical precipitation method and PVB-MnO2 nanocomposites were solution processed. The microwave absorption of PVB was enhanced by MnO2 nanorods compared to MnO2 nanospheres, for both X-band (8.2–12.4 GHz) and Ku-band (12.4–18 GHz). The lowest reflection loss (RL) of PVB-MnO2 nanorod composites was found to be - 37 dB with a large bandwidth at the thickness of 2 mm while PVB-MnO2 nanosphere composites show almost a linear decrease of RL with a minimum value −10 dB. It was observed that the enhancement of electromagnetic attenuation constant (α) and dielectric loss is the major factor responsible for the enhanced microwave absorption of PVB-MnO2 nanorod composite. Further, morphology controls the microwave absorption property of PVB-MnO2 nanocomposites through effective permittivity, degree of EM impedance matching (Δ), antenna mechanism, and dielectric dissipation that enhances high loss factor (LF %). The obtained high LF (84%) of PVB-MnO2 nanorod composite indicates the excellent microwave absorption property and can be treated as a novel coating polymer nanocomposite for microwave absorption based applications. © 2017 Elsevier Ltd