On 29 December 2008, the Council of Undang proclaimed him as the 11th
Yang di-Pertuan Besar of Negeri Sembilan succeeding
Tuanku Ja'afar who had died on 27 December 2008. Many prominent Malaysians backed Tuanku Muhriz to succeed as the Ruler of Negeri Sembilan in view of his modest and dignified personality and by the fact that he had a successful corporate career. He was also the rightful heir, by tradition, to the throne on the death of his father. Due to having kept a low profile, Tuanku Muhriz was largely unknown outside royal circles in
Negeri Sembilan. However, Tuanku Muhriz was not an underdog in the negotiations that was played out for the position of Yang di-Pertuan Besar. During the closed discussions to elect the successor to Tuanku Ja'afar, 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 Ja'afar's eldest son, instead as the next Ruler of Negeri Sembilan. Throughout his life Tuanku Muhriz 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. He also has powerful backers within the political establishment in the state, with the former
Menteri Besar Tan Sri
Mohd Isa Abdul Samad among his supporters. His supporters at both state and federal levels have quietly promoted him as a well-spoken, well-educated man—someone with the character to move past 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 Ja'afar's family, Tuanku Muhriz shuns publicity and though he can be very progressive in his outlook, he seems more rooted in traditional ways. Tuanku Ja'afar's family were 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.
2026 Negeri Sembilan royal and political crisis On 19 April 2026 at the Balai Undang Luak Sungei Ujong, the Undang Yang Empat announced the removal of Tuanku Muhriz due to alleged misconduct and named Tunku Nadzaruddin, the Tunku Panglima Besar of Negeri Sembilan and the third son of Tuanku Ja'afar, as the 12th Yang di-Pertuan Besar. However, the Negeri Sembilan state government rejected the declaration as Dato'
Mubarak Dohak, who signed and read the declaration, had no authority as Undang of Sungei Ujong after he was removed from the position effective 13 May 2025 for 33 alleged offences of the traditions and customary laws. On the following day, the four Undang claimed that Mubarak's removal was not valid as the DKU members who were present during the special session did not make a decision on the matter and that the other three Undang did not agree with Mubarak's removal. On 27 April, 14 assemblymen from
UMNO withdrew their support to Menteri Besar Datuk Seri
Aminuddin Harun of the
Pakatan Harapan coalition, citing that Aminuddin did not consult UMNO over the dispute between the Undang and Tuanku Muhriz. Negeri Sembilan UMNO later announced that they have accepted
Perikatan Nasional's collaboration and have a simple majority to form the state government. Aminuddin said that he was informed by Tuanku Muhriz to continue his duty as Menteri Besar until there is resolution over the matter.
Prime Minster Anwar Ibrahim reaffirmed Tuanku Muhriz's stance after being granted an audience and also said that a state snap election is unlikely to happen. On 30 April, the 14 UMNO assemblymen reaffirmed their support for Aminuddin to ensure political stability. == Colonel in Chief ==