In this work, two novel ruthenium-based compounds containing mercaptothiazolinate ligands were synthesized. A methanol (MeOH) solution containing [RuCl2(PPh3)3], 2-mercaptothiazoline (Hmctz) or 2-mercaptobenzothiazoline (Hmcbtz) (ligand/Ru=2) and triethylamine (NEt3) was refluxed leading to the formation of neutral complexes with the general formula cis-[Ru(N–S)2(PPh3)2] (N–S=mctz− – complex 1; N–S=mcbtz− – complex 2). We used NMR (1H and 31P{1H}), vibrational spectroscopy (FTIR), and elemental analysis to analyze these two complexes. Cyclic voltammetry revealed that complexes 1 and 2 underwent a reversible one-electron process due to the Ru(III)/Ru(II) pair. Reactivity of the complexes 1 and 2 with dmso leading to the substitution of one PPh3 by dmso was observed (complexes 3 and 4). Complex 1 showed higher antimicrobial activity against Gram (+) and Gram (−) bacteria (Bacillus subtilis and Escherichia coli, respectively). The formation of complex [Ru(mctz)2(dmso)(PPh3)] (3) was faster than complex [Ru(mcbtz)2(dmso)(PPh3)] (4) and this may account for the higher antibacterial activity of complex 1. Single-crystal X-ray diffraction furnished the molecular structures of complex 1 and of the product of its reaction with dmso, [Ru(mctz)2(dmso)(PPh3)] (3).