Cyclometalated mixed ligand platinum(II) complexes containing 2-phenylpyridine (ppyH) and pyridine carboxylic acids (PCAs), namely picolinic (2-pyacH), nicotinic (3-pyacH) and isonicotinic (4-pyacH) acid, with the general formula trans-N,N-[Pt(ppy)(PCA)Cl] [PCA = 2-pyacH (2), 3-pyacH (3), 4-pyacH (4)] were synthesized and characterized. The crystal structures of the complexes 3 and 4 showed that the PCAs coordinated in a trans-position towards the orthometalated ppyC, forming hydrogen-bonded homodimers through their carboxylic groups. NMR spectroscopic techniques were used to identify the solution-structural features of the complexes 2–4. The results revealed that the dihedral angle (γ) between the PCA plane and the plane of ppy depends on the carboxylic substitution of the pyridine ring and, in the cases of 3 and 4, the solid-state characteristics were retained. All complexes emit similarly in degassed solution of acetone (475–580 nm) with a very low quantum yield (Φ ∼ 0.05–0.17 %), while in the solid state, a green emission centered at about 530 nm with Φ varying from 3.20–4.86 % is produced.