Display omitted •Precise design of Pd-decorated vertically aligned ZnO nanorod architectures.•Pd@ZnO sensors exhibit excellent selectivity towards C2H5OH @260 °C.•C2H5OH performance of ZnO sensor increased by the order of 4 after Pd-decoration.•Excellent C2H5OH response reproducibility of Pd@ZnO sensors @260 °C.•Plausible gas sensing mechanism of Pd@ZnO sensors is proposed. The development of defined hierarchical transition metal oxide nanostructures has attracted remarkable attention due to their superior chemiresistive gas sensing performances. In the present study, vertically aligned zinc oxide nanorods (ZnO-NRs) were grown by chemical vapor deposition (CVD) and precise decoration with palladium nanoparticles (Pd-NPs) on their surfaces, at different deposition times, was done through unique RF magnetic sputtering followed by annealing. The effect of different Pd-NPs loadings on structure, surface morphology, elemental composition, and chemiresistive C2H5OH gas sensing properties of CVD-mediated pristine ZnO-NRs was elucidated thoroughly and accounted. As-fabricated pristine and Pd-loaded ZnO-NRs sensors are sensitive towards ethanol (C2H5OH) at 260 °C. Moreover, gas sensing investigations revealed that the C2H5OH response of pristine ZnO NRs was enhanced strongly due to Pd-decoration. Such a response enhancement is mainly attributed to the catalytic activity of Pd-NPs. It is confirmed that the influence of Pd-NPs on ZnO-NRs sensor is normally to strengthen the amount of chemisorbed oxygen on ZnO-NRs surface and enhance the C2H5OH response. Present work can motivate research advancement on precise designing of innovative one dimensional and related nanostructures for the application of selective chemiresistive gas sensors.