He was educated at the Alor Merah Malay School and continued his studies at the Sultan Abdul Hamid College.

On 12 February 1964, he was commissioned as a lieutenant and stationed with the 2nd Battalion of the Royal Malay Regiment in Pengkalan Chepa, Kota Bharu, Kelantan.

He replaced Tunku Abdul Malik who died of natural causes on 29 November 2015 at Sultanah Bahiyah Hospital in Alor Setar.

[4] As Raja Muda, Sallehuddin held a number of important positions including as chancellor of the Cyberjaya University College of Medical Sciences and president of the Kedah Islamic Religious Council.

He was officially enthroned as sultan on 22 October 2018 and was awarded the sobriquet Al-Aminul Karim in a televised ceremony, the first since 1959, at the Istana Anak Bukit's Balai Besar.

As per his duties as sultan and head of the state of Kedah, he currently serves as the Colonel-in-chief of the Royal Malay Regiment.