Prince Mateen of Brunei

On 9 May 2010, Prince Mateen began his Commissioning Course for Regular Army Officers along with 200 recruits in Royal Military Academy Sandhurst.[4][5] On 15 April 2011, Prince Mateen graduated from the commissioning course as an officer cadet of the Royal Military Academy Sandhurst, United Kingdom and promoted to the rank of Second Lieutenant.[5] According to a Borneo Bulletin report, Mateen was promoted to a rank of a Substantive Lieutenant later on 9 July 2012.[6][5] His promotion ceremony to Acting Captain was held on 31 August 2016 and would come into effect on 9 May later that year.[7] On 28 April 2017, he completed a seven-month Elementary Flying Training at RAF Cranwell,[5][2] and later in March 2018, Prince Mateen was qualified as a helicopter pilot in Defence Helicopter Flying School at RAF Shawbury, in which his father awarded him his flying brevet (wings).[2] On 30 June 2019, as part of the celebrations honoring the 58th anniversary of the Royal Brunei Armed Forces (RBAF), his father gave his permission to grant him honorary membership in the Special Forces Regiment.[8]

On 20 May 2021, Prince Mateen was promoted to the rank of Major.[9] Later that year, Prince Mateen had undergone the The All Arms Commando Course (AACC) at the Commando Training Centre Royal Marines (CTCRM) in the United Kingdom for eleven weeks from the 20th of September to the 2nd of December, where he received the Green Beret.[10][11] The RAF reported that he had spent the previous two weeks training alongside 64 other new parachutists. Once he completed the Basic Parachute Training on 23 September 2022, the award ceremony was held at RAF Brize Norton.[12]

Following leaders' bilateral meetings in Amman on 4 October 2018, which saw the signing of three memorandum of understanding in the areas of infrastructure, tourism, and defense in addition to a customs cooperation agreement, Brunei and Jordan reaffirmed their longstanding alliance. The negotiations were held at Al-Husseinieh Palace with participation from senior cabinet members from both nations as well as Prince Mateen and Crown Prince Al Hussein.[13] Later on 19 October, him alongside his father attended the 12th Asia–Europe Meeting (ASEM) in Brussels, where Brunei demanded that talks to get back up a Free Trade Agreement (FTA) between the European Union (EU) and ASEAN.[14]

On 22 October 2019, saw the culmination of Japan's Emperor Naruhito's succession to the Chrysanthemum throne in a ceremony that embodied the majesty and traditions of a 2,000-year-old monarchy. Him alongside his father attended the rituals, which marked the culmination of a transition that began with his father's abdication earlier that year.[15] Later on 3 November, the 35th ASEAN Summit and Related Summits' Opening Ceremony was attended by both father and son at Muang Thong Thani.[16] On 19 September 2022, he and his father were present at Westminster Abbey for Her Majesty Queen Elizabeth II's state burial.[17]

From 13 to 14 March 2023, Prince Mateen took part in a comprehensive tour of the Coronado, California-based Naval Special Warfare (NSW) commands. He met with members of NSW and Rear Admiral Keith B. Davids, chief of Navy Special Warfare Command, to talk about potential areas of future cooperation. A description of the human performance program at NSWG-1 was also given to him. The program employs a holistic approach to coordinate resources for the best performance and recovery. It includes strength and conditioning training, sports medicine, performance psychology, performance nutrition, and research and technologies related to human performance.[18] Once again along with his father, he went to the signing of the marriage contract, the royal solemnization ceremony, and the feast and celebration held in honor of Prince Al Hussein bin Abdullah II and Rajwa Khalid Alseif's royal wedding on 1 June.[19]

Prince 'Abdul Mateen has represented his country in polo at the 2017 and 2019 Southeast Asian Games.[20] Nearly 3,000 spectators came to watch the polo game between Brunei and Malaysia during the 2017 SEA Games, with notably him and his sister, Princess Azemah facing off Malaysian Minister Khairy Jamaluddin.[21][22]

On 7 April 2007, the AM Gunners captained by Abdul Mateen ended in a 1–1 draw against team Projek Ikan Pusu (PIP) during a Charity football match. The match which took place at the Hassanal Bolkiah National Stadium collected a total of B$12,192.[23] A charity match between Mateen-led AM Gunners and Sport School was again held at the same location on 22 March 2008.[24]