Teo joined in the Singapore Armed Forces (SAF) in 1972 and was commissioned as a naval officer at the SAFTI Military Institute in 1973. He went on to hold various command and staff appointments in the Republic of Singapore Navy (RSN) and the Joint Staff before his appointment as Chief of Navy in 1991 with the rank of Rear-Admiral (Two-Star) before leaving the SAF on 7 December 1992 to contest in the 1992 by-elections in Marine Parade GRC.
