We evaluated the effects of the pollens of transgenic Chinese cabbage (Brassica campestris subsp. napus var. pekinensis Makino), expressing Bacillus thuringiensis Cry1Ac toxin (Bt cabbage), on Bombyx mori larvae. Decreased survival rate and body weight of B. mori larvae were observed when fed with an artificial diet containing Bt cabbage pollens. ELISA test using Cry1Ac-antibody revealed that the Cry toxin was detected not only in the alimentary canal but also in the hemolymph and remaining body parts, suggesting that the ingested Cry1Ac protein is distributed inside the body likely through the damaged midgut epithelial membrane of B. mori. Taken together, our results suggested that Bt cabbage pollens adversely affect non-target insect B. mori larvae when consumed. Considering the low possibility of Bt cabbage pollen exposure to B. mori in the actual field condition, however, the risk would be minimal.