Ethnically Hutu, he worked as an agronomist for the Belgian colonial administration in Ruanda-Urundi before starting a successful market garden in Bugarama.

He was a leading member of Louis Rwagasore's political party, the Union for National Progress (UPRONA), and in 1961 served as the organisation's interim president.

His criticism of Muhirwa and his successor led him to be arrested on several occasions, but in 1965 he was elected to a seat in the National Assembly representing the Bujumbura constituency.

Dissatisfied with this, he quit his job and established a market garden to support farmers in Bugarama and arranged for their produce to be transported to Usumbura for sale.

During this time he began making public demands for reform, appealing to King Baudouin of Belgium to assist peasants in 1955,[b] denouncing administration manipulations of royal domains in 1958, and criticising colonial paternalism in 1959.

[2][3] That year he published a political manifesto, Mbire gito canje... (Listen my son...) in which he called for respect of tradition and stressed the important of reciprocity in relationships between members of different castes in Urundi's social hierarchy.

[17] His death stoked divisions in UPRONA, and fueled a rivalry between Mirerekano and the new Ganwa prime minister, André Muhirwa.

[20] In an attempt to overturn the outcome of the UPRONA leadership dispute, Mirerekano called a mass meeting of party members at Rwagasore Stadium in Bujumbura on 26 August.

[21] Before a crowd of approximately 2,000 people, he angrily denounced the Muhirwa Government for nepotism and displays of ethnic favoritism, and accused it of betraying Rwagasore's wishes.

[22] At Mwami Mwambutsa IV's intervention, an UPRONA mass congress was held in September to resolve the leadership dispute, which led to both Mirerekano and Muhirwa being assigned vice presidencies in the party.

[19] Unsatisfied with the results of the congress, Mirerekano refused to attend any meetings of the newly-constituted central committee and organised his own UPRONA wing, of which he became president.

He also called for a renewed investigation into Rwagasore's murder, and accused Muhirwa of opposing this because he was from the same Ganwa clan as the implicated perpetrators.

[1] Mirerekano, believed to have helped plan the coup attempt, was arrested by the government, tried by military tribunal, and executed[4][28] on either 19 or 25 October.