Shaikh Harun Mustafa read law at the University of Leeds and graduated with a Bachelor of Laws Degree with Honours and returned back to Malaysia to complete the Certificate of Legal Practice.

He was called to the Malaysian Bar on 7 February 1995. Where prior to that he undertook his pupillage at Messrs. Lainah Yow & Zur.

Whilst in the firm of Lainah Yow & Zur, he was seconded to Indah Water Konsortium to provide Legal Services, whereupon he later accepted an offer to work with Indah Water in their Legal Department. Indah Water Konsortium is the national concessionaire for sewerage services

It was here that he started his interest in technology related matters and the environment.

As a lawyer, he has more than a decade of experience in corporate work, and has experience in litigation and secretarial work. Apart from drafting and vetting many different types of agreements ranging from construction contracts, consultancy agreements, aviation purchases and leases, corporate loans, both conventional and Islamic, to agency and service agreements, joint ventures, mergers and acquisitions and he has also assisted in drafting government regulations. Whilst at Indah Water, he also had the opportunity to be involved in negotiations with State Authorities and Federal Government Officers in addition to providing advise to the management.

His work as a lawyer has also brought him round the world where he has acted for clients in the United States, Indonesia, Philippines, China, India and Ghana for commercial transactions.

Shaikh Harun has also obtained a certificate of shipping practice issued by the Institute of Shipping in Singapore. He has also embarked in the niche area of aviation practice where he acts for certain clients-handling matters from the purchase of the aircraft, financing, registration of the aircraft and leasing of the aircraft in both Malaysia and Indonesia.

In the technology sector, Shaikh Harun is a director in Datasonic Innovation Sdn Bhd, a subsidiary of Datasonic Berhad, a company listed on Bursa Malaysia. The company is primarily involved in biometric solutions.

He has also a stake and is a director of Prathista (South East Asia) Sdn Bhd, a company that is into innovative Agricultural Fertilizers & Nutraceuticals, which is a subsidiary of Prathista Industries Limited from India