He began his career in an international bank in Malaysia and became a director and shareholder of a company licensed as brokers in interbank foreign exchange and in the currency deposits market(1973–1986). He was the chairman and shareholder of a Malaysian joint venture with a worldwide advertising agency (1981–1992), chairman and director of a joint venture company involved in the manufacturing of building products(1995–1998) and a director and shareholder of a company engaged in electrical engineering and construction (1995 to present). He has been on the board of directors of Bangkok Bank since 2006.
The Negeri Sembilan Constitution states that the order of succession should first be the sons of the previous Ruler, followed by the grandsons of the previous Ruler, then by the brothers of the previous Ruler, and only then by the sons of the brothers of the previous Ruler.
Tuanku Muhriz was first in the order of succession before the death of Tuanku Munawir, followed by Tunku Jaafar and Tunku Abdullah. When Tuanku Munawir died, Tuanku Muhriz was not chosen. Instead the council chose his half-uncle Tuanku Jaafar ibni Almarhum Tuanku Abdul Rahman, a diplomat. It has been suggested that the then Prime Minister of Malaysia, Tunku Abdul Rahman, influenced the Undangs not to choose Tuanku Muhriz on account of his youth (he was then only nineteen).
Due to a lifelong habit of keeping a low profile, Tuanku Muhriz was largely unknown outside royal circles in Negeri Sembilan. However, Tuanku Muhriz was hardly the underdog in the intense negotiations that was played out for the position of Yang di-Pertuan Besar of Negri Sembilan. During the closed discussions to elect the successor to the late Tuanku Jaafar, at least two, if not all four of the Undangs strongly championed his candidacy. They refused to budge when it was suggested that they consider Tunku Naquiyuddin, Tuanku Jaafar's eldest son, instead as the next Ruler of Negeri Sembilan.
Tuanku Muhriz has throughout his life established and maintained strong ties with the Undangs, the general nobility, the lesser royalty and people of Negeri Sembilan, and more so since moving back to the state a few years ago. He also has powerful backers within the political establishment in the state, with the former state Menteri Besar Tan Sri Isa Samad among his supporters.
There has been a quiet campaign by his loyal supporters at state and federal level to portray him as a well-spoken and well-educated man; someone who had the great strength of character to put aside the disappointment of not being appointed Ruler of the state in 1967: and who continues to lead a dignified and respectable life.
His supporters said that in contrast to members of Tuanku Jaafar's family, Tuanku Muhriz shuns publicity and though he can be very progressive in his outlook, he seems more rooted in traditional ways. Tuanku Jaafar's family are said to be completely devastated with the decision of the Undangs to select Tuanku Muhriz over Tunku Naquiyuddin. They too had several powerful politicians in their camp but the Undangs were not to be swayed.