Bacillus thuringiensis is an anaerobic, spore forming bacterium that produces various toxic proteins both during its vegetative stage and sporulative stage. During its sporulative stage, it produces parasporal proteins that have long been used in the agriculture fields as insecticides. Although anticancer effect of Bacillus thuringiensis parasporal proteins can be dated back to the 1970s, research in this area went through a giant leap in the late 1990s, with much of the work being done in Japan. It has been found that some strains of non-insecticidal Bacillus thuringiensis produce parasporal proteins that exhibit anticancer activity. Due to their selectivity against human cancer cells but not normal cells, some of these proteins have been extensively studied for their anticancer effect and the mechanism of action by which these proteins kill cancer cells have also been widely explored in Japan and Malaysia with sporadic reports from other parts of the world. The abundance of these bacilli in nature and their selectivity have made them potential candidates for cancer treatment. However, literature on the in vivo effect of these proteins is scarce. Since different Bacillus thuringiensis strains produce different cytotoxic proteins with wide variations in their anticancer effect and mechanism of action, further investigations are necessary and their effect in vivo must be well established before they can be used in human subjects.