His father was of Eko Division of Lagos origin and was a member of the Royal West African Frontier Force during World War II.

Mobolaji Johnson also attended the Mons Officer Cadet School in Aldershot and the Royal Military Academy, Sandhurst, United Kingdom, between 1960 and 1961.

Ironsi was the head of state and wanted someone from Lagos to handle some of the problems of the federal territory.

Johnson's administration was responsible for the demolition and disinterment of people buried at Ajele Cemetery such as Samuel Ajayi Crowther, James Pinson Labulo Davies, Madam Tinubu, Thomas Babington Macaulay, and many others.

Peel noted that the demolition had deprived "Lagosians not only of a precious green space in the heart of the city but of the memorials of their forebears".

[9] Nobel Laureate Wole Soyinka called the demolition "the violation of that ancestral place" noting that "the order came from the military governor [Mobolaji Johnson]: 'Dig up those dead and forgotten ancestors and plant a modern council building – with all its lucrative corollaries on that somnolent spot".

[10] In 1975 at the inception of the General Murtala Mohammed administration Johnson was one of the two state Governors (along with Brigadier General Oluwole Rotimi) found not guilty of corruption by the three-man panel commissioned to investigate the various allegations of corruption amongst the State Governors.

A road, an avenue, and a sports complex in Mobolaji's home state bear his name as well as a Housing Scheme at Lekki both in Lagos.