Five undescribed 12-membered macrolides containing thioethers, thiocladospolides F-J, together with the known biogenetic related analogues, were isolated from a mangrove-derived endophytic fungus Cladosporium oxysporum. The absolute configuration of thiocladospolide F was deduced by single-crystal X-ray diffraction, and those of thiocladospolides G-J were determined based on specific optical rotation and electronic circular dichroism (ECD) data, as well as the biogenetic considerations. Thiocladospolide G display the best antimicrobial activity against the aquatic pathogen Edwardsiella tarda with minimal inhibit concentration (MIC) value of 4 μg/mL.