Electrochemotherapy (ECT) is a new therapeutical technique that combines the administration of trains of biphasic pulses with the local application of poorly permeant anticancer molecules, thus obtaining increased chemotherapy uptake. The purpose of this study was to prospectively assess the adjuvant potentialities of ECT for the treatment of different incompletely excised canine sarcomas. Twenty-two privately owned dogs with incomplete surgical excision of high grade sarcomas were treated with bleomycin injected within the tumor bed (1.5 IU/mg) followed by the sequential application of trains of biphasic pulses (8 pulses, 1300 V/cm, 50+50 micros duration, 1 Hz frequency). The overall response rate was 95% (21 out of 22 patients) with a mean time to recurrence of 730 days. At the time of writing 11 dogs were still in remission, three dogs had died of unrelated causes, one had local recurrence and the owner declined further treatment, one had limb amputation following recurrence, four had both local recurrence and distant metastases that led to euthanasia, and two were retreated following tumor recurrence and are disease free at 850 and 1947 days. The only observed toxicity was wound dehiscence in three patients. Electrochemotherapy is well tolerated and has effectiveness against incompletely excised sarcomas in companion animals. Further investigations are warranted to improve the currently available protocols.