Mixed-ligand metal-polymer complexes (MPC) of N-vinylpyrrolidone-N-vinylformamide-N-vinyl iminodiacedic acid (VP-VFA-VIDA) copolymers and diethyldithiocarbamate (DEDTC) as a co-ligand with indium were synthesized under mild conditions and pH close to physiological values. Isolated MPC were characterized by UV, IR, ¹H NMR, atomic absorption spectrophotometry, and HPLC. The obtained data implied that the MPC contain 8–10 wt% of (IDA)In(DEDTC) fragments. The optimal conditions for radiochemical synthesis of VP-VFA-VIDA-¹¹¹In-(DEDTC) metal-polymer complex with mixed ligands were defined. The closest coordination environment of ¹¹¹In was studied by perturbed angular correlation technique. The obtained data are in good agreement with the information about weight amounts of the corresponding indium MPC.