Lieutenant Colonel Aldi bin Haji Hassan joined the Royal Brunei Armed Forces on 22nd February 1997. He underwent his Officer Cadet Training at the Singapore Armed Forces Training Institute in October 1997 and was commissioned as 2nd Lieutenant in October 1998.
After commissioning, Lieutenant Colonel Aldi's first assignment was as Platoon Commander of 'A' Company, First Battalion Royal Brunei Land Force (A Coy 1Bn RBLF). Throughout his service, Lieutenant Colonel Aldi also held various appointments, namely as Officer Commanding of Special Task Platoon (STP) 1Bn RBLF from 2000 to 2003, Staff Officer Grade 3 Training at RBLF Headquarters from 2003 to 2004, Second-in-Command of Course Company Training Centre RBAF from 2005 to 2008, Officer Commanding of Officer Cadet School RBAF from 2008 to 2009, Officer Commanding of 'C' Company 1Bn RBLF from 2009 to 2011, Officer Commanding of School of Infantry, Training Institute RBAF from 2011 to 2014, Acting Chief of Instructor, Training Institute RBAF in 2015, Commanding Officer of 1Bn RBLF from 2015 to 2018, Assistant Chief of Staff Admin and Personnel RBLF from 2018 to 2019 and Deputy Commandant, Training Institute RBAF from 2019 to 2021. He was appointed as the Chief of Staff RBLF on 01 November 2021.
From 2004 until 2005, Lieutenant Colonel Aldi was one of the selected members of the Brunei Contingent in International Monitoring Team (IMT) in Mindanao, Philippines. After he came back from the mission, Lieutenant Colonel Aldi was conferred with Pingat Jasa Kebaktian - PJK (Meritorious Service Medal) and in 2019 he was bestowed with Darjah Setia Negara Brunei Yang Amat Bahagia Darjah Keempat - P.S.B (Most Blessed Order of Setia Negara Brunei 4th Class).
Lieutenant Colonel Aldi attended various military courses such as Platoon Commander Course at Pusat Latihan Tentera Darat (PULADA) Malaysia in 2000, Light Role Reconnaissance Commander at School of Infantry Warminster United Kingdom in 2001, Jungle Warfare Tracking Instructor Course at Training Team Brunei (TTB) Seria in 2002, Company Tactic Course (SUSDANKI) in Pusat Pendidikan Infantri (PUSNIKIF) Indonesia in 2009, Battalion Tactics Course at Singapore Armed Forces Training Institute (SAFTI) in the Republic of Singapore in 2011 and Command and Staff Course at Defence Academy RBAF in 2013. He has also attended the Executive Development Programme at the Ministry of Defence, Brunei Darussalam in 2018.
Lieutenant Colonel Aldi is an all-round sportsman, especially in football and golf. Lieutenant Colonel Aldi is married to Dayangku Noor Hafidzah binti Pengiran Haji Ahmad and is blessed with four boys and three daughters.