Four new Zeises family ions with mixed-halide ligands, i.e., PtClnX3-n(C2H4)(-) (X = Br, I; n = 1, 2), were synthesized via ligand-exchange reactions of KX salts with KPtCl3(C2H4) in aqueous solutions, and were detected in vacuum via electrospray ionization mass spectrometry. Their photoelectron spectra reveal a series of well-resolved spectral peaks with their electron binding energies (EBEs) decreasing with increasing halide size, with I having a much stronger effect than Br, i.e., 4.57 (-CI3) > 4.56 (-Cl2Br) > 4.53 (-ClBr2) > 4.34 (-Cl2I) > 4.30 eV (-ClI2). Ab initio electronic structure calculations including spin orbit coupling (SOC) predict that the cis- and trans-isomers are nearly isoenergetic with the cisisomer for -Cl2X and the trans-isomer for -CIX2 slightly favored, respectively. Excited-state spectra calculated with time-dependent density functional theory (TDDFT), and their comparison with the observed ones, suggest that for each species both the cis- and trans-configurations coexist in the experiments and contribute to the observed spectra, a fact that clearly deviates from the prediction of the widely accepted trans-effect, which suggests that only one isomer would have formed.