Natural biomaterials, such as chitosan and collagen, are useful for biomedical applications because they are biocompatible, mechanically robust and biodegradable, but it is difficult to rapidly and tightly bond them to living tissues. Here, we demonstrate that the microbial enzyme transglutaminase (mTG) can be used to rapidly (< 5 min) bond chitosan and collagen biomaterials to the surfaces of hepatic, cardiac and dermal tissues, as well as to functionalized polydimethylsiloxane (PDMS) materials that are used in medical products. The mTG-bonded Shrilk patches composed of a chitosan-fibroin laminate effectively sealed intestinal perforations, and a newly developed two-component mTG-bonded chitosan spray effectively repaired ruptures in a breathing lung when tested ex vivo. The mechanical strength of mTG-catalyzed chitosan adhesive bonds were comparable to those generated by commonly used surgical glues. These results suggest that mTG preparations may be broadly employed to bond various types of organic materials, including polysaccharides, proteins and functionalized inorganic polymers to living tissues, which may open new avenues for biomedical engineering, medical device integration and tissue repair.