Cation vibronic spectra are measured for 1,4-benzodioxan (BZD) and van der Waals complexes of BZD with one and two Ar atoms using zero electron kinetic energy and mass analyzed threshold ionization spectroscopy. The spectra of the monomer cation were used to measure the frequencies of the two key low-frequency modes which had previously been extensively studied in the neutral S-0 and S-1 states. The aliphatic ring twisting mode, nu(25), has an energy of 146 cm(-1) in the cation, intermediate between the values found in the S-0 and S-1 states. The bending, butterfly-like mode nu(48) has an energy of 125 cm(-1), which is of higher frequency than either of the neutral states. The S-1 spectra of the BZD-Ar-1 and BZD-Ar-2 complexes are recorded and observed to have modest red shifts from the monomer. The cation spectra of the complexes are also measured using mass analyzed threshold ionization spectroscopy including scans at higher energy which are used to determine the Ar binding energies. The energies for the loss of one Ar atom were determined to be 630 +/- 10 and 650 +/- 10 cm(-1) for BZD-Ar and BZD-Ar-2, respectively. The similar cation spectra and similar binding energies indicate that each Ar atom in BZD-Ar-2 has a similar binding geometry. Quantum chemical calculations were performed which had fair agreement with the measured binding energies and give some insight into the specific binding geometry.