A low-temperature chemical bath deposition (CBD) technique has been used for the preparation of Mn3O4 thin films on glass substrates. The kinetic behavior and the formation mechanism of the solid thin films from the aqueous solution have been investigated. Structure (X-ray diffraction and Raman), morphological (atom force microscope), optical (UV-visible and near infrared), and magnetic characterizations of the deposited films are presented. The results indicate that the deposited Mn3O4 thin films of smooth surface with nanosized grains are well crystalline and display the size-dependent optical and magnetic properties.