Regarding thalidomide's effects in cancer and the problems related to its physicochemical characteristics and toxic effects, we proposed a new biodegradable polymeric implant to this drug. In this paper, we evaluate the antiangiogenic activity and antitumor effect of thalidomide when incorporated in poly-lactide-co-glycolide (PLGA) implants in an animal model for Ehrlich tumor. This dosage form permits the prolonged drug release. The biodegradable implants could reduce the blood vessel in a chorioallantoic membrane (CAM) model. When applied to the Ehrlich tumor model, implant also showed to reduce the number of vessels. It was also observed to reduce areas of inflammation and increases the area of necrosis in the group of thalidomide implant. A 47% reduction in tumor volume was observed in the thalidomide implant group, which is discussed in relation to literature reported results of thalidomide conventional administration ways.