In this study, a new Manganese (II) complex with tartaric acid (C 4 H 6 O ) and 1, 10-phenanthroline (C 12 N 2 H 8 6 ) ligands were synthesized and characterized using various Physico-chemical (molar conductance, solubility test, and melting point gravimetric analysis) and spectroscopic techniques (FTIR, UV-Vis). Based on the Physico-chemical and spectroscopic data octahedral geometry were proposed for both of complexes. Moreover, in - vitro antibacterial activity was also tested on two Gram positive (S. aureus, S.epidermidis) and two Gram negative (E. coli and K. pneumonia) bacteria using disc diffusion method [Mn (C 4 H 5 O 6 ) phen] complexes showed better activities on Streptococcus epidermidis than the other bacteria. The free ligand 1, 10-phenanthroline demonstrated better activity than other complex and ligands in all types of bacteria. Thus, after cytotoxicity and in vivo test, these complexes may be used as alternative drug against the above mentioned bacteria. 2