Sunmonu briefly attended a primary education in Ghana before following his paternal grandmother and mother back to Nigeria where they settled at Osogbo.
[2] As a young student, he and his twin met Alake Ladapo Ademola who was then in exile in Osogbo.
[4] Sunmonu completed his education with a diploma in civil engineering from Yaba College of Technology.
Sunmonu was elected president of the newly formed Nigerian Labour Congress in 1978.
Prior to the union's formation, the Obasanjo government had disbanded four national labour centers, including the moderate United Labour Congress led by Haroun Adebola and the more radical Nigeria Trade Union Congress.