MTSI Views 8 meanings found MTSI can refer to the Mock Trial Summer Institute, a program for aspiring litigators, or to a range of technology and communications firms offering services from micro‑technology to microwave transmission. Governmental Mock Trial Summer Institute Computing Micro Technology Services Inc Marshall Technology Solutions Inc Modern Technology Solutions Inc Business Microwave Transmission Systems Inc Mendenhall Technical Services Inc Moseley Technical Services Inc Micro Touch Systems, Inc.