The electrodeposition of Tl2O3/Co3O4 composites has been performed by anodic oxidation of Tl+ ions in the presence of suspended Co3O4 particles. This study, aimed at obtaining and characterizing new electrocatalytic materials for oxygen evolution reaction, has shown that Co3O4 particles enhance the rate of nucleation and growth of the Tl2O3 matrix. At each potential, induction times are shorter and kinetic constants are higher in the presence of Co3O4 than in its absence. The chronoamperometric transients measured during composite deposition are compatible with instantaneous nucleation and 3D growth. Scanning electron microscopy and energy dispersive X-ray analyses data show that Co3O4 particles become effectively embedded in the deposit from the early stages of its formation and act as centers of preferential growth for the matrix, so that the Co3O4 content is higher near the electrode/composite interface than in the bulk. Tl2O3/Co3O4 composites are compared with other systems for which nucleation and growth of the matrix is unaffected by the dispersed phase.