Two biodegradable polymers, poly(L-lactide) (PLLA) and cellulose acetate (CA), were solvent-cast-blended with chloroform. Macrophase separation took place without a compatibilizer. However, homogeneous blend films were obtained with the addition of tetraisopropyl titanate (TP) as a compatibilizer to the blend. We investigated the reasons for the blends exhibiting homogeneity and measured the physical properties of the blends. We reached the following conclusions: (1) the addition of TP produces small PLLA crystallites in the PLLA/CA blends, (2) the addition of TP reduces the thermal decomposition temperature of PLLA/CA blends, (3) Young's modulus of the blends is almost independent of the blend ratio, and (4) the introduction of TP assists with the hydrolysis of the blends.