He obtained a scholarship to study law at the Institute of Administration, now Ahmadu Bello University, Zaria, followed by legal studies in the United Kingdom.
He was called to the English Bar in 1963, Nigerian Bar in January 1964 and joined the Ministry of Justice where became a Senior State Counsel in 1968.
In 1969, he set up in private practice in kano but was appointed a judge of the Federal Revenue Court in 1974. In January 1977, he was elevated to the Court of Appeal Bench. In 1992 he was made President of the Nigerian Court of Appeal, a position he held until retiring in 1999.His son is also a successful Lawyer, becoming Chairman of the Nigerian Bar Association, Ilorin Branch.
In 2000 President Olusegun Obasanjo appointed Akanbi as Chairman of the newly established Independent Corrupt Practices Commission (ICPC). Four years later, the ICPC had failed to make any significant convictions. Akanbi publicly questioned why the government had set up the ICPC and appointed competent people to run it “only to frustrate it from performing by starving it of funds”. He said that another issue was that the law forbade it from investigating corrupt practices dating before the creation of the ICPC.
In March 2004, Justice Mustapha Akanbi urged parliamentarians to ratify the United Nations and the African Union Conventions Against Corruption, which would greatly assist the struggle against corruption.
As of July 2005, the ICPC charged 85 people but had only secured two corruption-related convictions. Commenting on this record, Akbani said he suspected that some judges had been paid off to toss out cases. In September 2005 Akanbe said, “Corruption has been described as a cankerworm, a malaise that has afflicted our nation and done havoc to our corporate existence”. He attributed the problem to lack of will by past military leaders to fight corruption, inconsistency in government policies, and reluctance by law enforcement agencies to arrest and prosecute “sacred cows”.
Akanbi retired in 2005 on completion of the first term of office, and was succeeded by Emmanuel Ayoola. He joined the board of the Justice and Law Enforcement Reformation Organization, a non-profit organization that aims to eradicate corruption and poverty from the perspective of the Judiciary and Law Enforcement agencies. In 2006, Akanbi established the Mustapha Akanbi Foundation in Ilorin, Kwara State, dedicated to strengthening civil society groups, governmental agencies and private business concerns and helping them imbibe a culture of transparency and accountability.
In August 2009 he called on Nigerian Muslims to shun the ideas of the Boko Haram sect, which teaches that non-Islamic education is a sin. He said that both Western and Islamic education were germane to the development of mankind.