The present work focuses on the synthesis and evaluation of the antimicrobial activity of ZnxMg1-xO solid solutions. ZnxMg1-xO solid solutions were synthesized through the thermal decomposition of ZnMg-precursor synthesized in aqueous and ethanol solutions via a two-steps process. The antimicrobial activity of ZnxMg1-xO solid solution against E. coli was evaluated using the spread plate method in presence of ZnxMg1-xO powder of different contents of Zn species, 'x'. The powder concentrations evaluated were 500, 1000, and 1500 ppm. Zn0.10Mg0.90O powders exhibited a bacterial growth inhibition between 38% and 100% when the powder concentration increased from 500 up to 1500 ppm, respectively. A decreasing trend was observed for x = 0.30 and above; the corresponding bacterial growth inhibition was 12%, 6%, and 5% when the particles concentration was, respectively, 500, 1000, and 1500 ppm. X-Ray diffraction analyses suggested the incorporation of Zn ions into the MgO lattice for 'x' values below 0.10, enhancing the antimicrobial activity; the formation of two isolated oxide phases observed at larger 'x' values (e.g. x = 0.30 and x = 0.50 Zn), could explain the detected inhibition of the corresponding antimicrobial activity.