This dataset is for the paper "Vibronic Effects on the Quantum Tunnelling of Magnetisation in Single-Molecule Magnets". It contains the computational inputs/outputs for the [Dy(Cpttt)2]+ cation embedded in two different balls of dichloromethane. The outputs give the optimised structure and vibrational modes (calculated with DFT), the electronic structure (calculated with CASSCF-SO), and the spin-phonon coupling. These data, along with the theoretical vibronic model described in the paper, allow us to show the vibronic contribution to quantum tunnelling of the magnetisation (QTM). We find that the overall effect is to increase QTM rates, however that some vibrational modes can in fact suppress QTM.