He started his legal career as a Judicial and Legal Service officer on 8 May 1978 and had since held various post, serving as Magistrate in Betong and Temerloh, Deputy Public Prosecutor for the state of Johor, DPP of Royal Malaysian Customs Department, State Legal Advisor of Perlis, Head of Prosecution Unit for Penang, Senior Federal Counsel of Ministry of Home Affairs of Malaysia and State Legal Advisor of Kelantan. In 1994, while serving as State Legal Advisor of Kelantan, he was admitted as advocate and solicitor in the High Court in Malaya at Kota Bharu. He was then transferred to the Attorney General's Chambers headquarters where he served as deputy director and later as Head of Division, Advisory and International Division of Attorney General's Chambers. On 1 October 1998, he became one of the seven persons who were appointed as Senior Deputy Public Prosecutor by the Attorney General of Malaysia. His last position in Judicial and Legal Service was Commissioner Law Revision and Reform Malaysia. On 1 June 2000, he was elevated to the High Court bench as judicial commissioner and was assigned to preside over High Court in Malaya in Malacca. On 1 March 2002, he was appointed as a High Court Judge and served in the High Court in Malaya in Malacca, Kuala Lumpur and Terengganu. His elevation to the Court of Appeal bench took place on 18 July 2007. On 10 August 2011, he took his appointment as Judge, Federal Court of Malaysia. On 1 April 2017, he was officially appointed as Chief Judge of Malaya, taking over from Zulkefli Ahmad Makinudin to occupy the third highest judicial office in Malaysia. Following the 14th Malaysian general election and the resignation of Zulkefli, Maarop was again chosen to take over from Zulkefli, this time ascending to the second highest judicial office of Malaysia, becoming the President of the Court of Appeal of Malaysia. He was sworn-in by the Yang di-Pertuan Agong on 11 July 2018. As such, Maarop is currently the second-highest judicial officer in Malaysia after the Chief Justice of Malaysia. Maarop retired as PCA on the 24 November 2019 having reached the mandatory retirement age as stipulated by the Constitution of Malaysia.
