Globacom Chairman Mike Adenuga Jnr, with interests in oil exploration and real estate has moved up, ranking next to Aliko Dangote as Africa's second richest man.
Forbes magazine said Adenuga's net worth rose tremendously from $5.3 billion to $9.2 billion.
He is now just $800million away from Dangote Group President Aliko Dangote, whose wealth dipped to $10 billion, from $12 billion last year.
However, Dangote retains the Africa's richest man title for the eighth consecutive time despite.
BUA Group Chief Executive Officer Abdulsamad Rabiu featured on the list for the first time since 2015.
The merger between Rabiu's Kalambaina Cement firm with the Cement Company of Northern Nigeria, which he controlled, in December, last year, was formally consummated in Sokoto earlier this week. He now owns 97 per cent of the entity.
Kalambaina, which operates a new cement production facility, started selling cement mid-last year just as Rabiu's OBU Cement has expanded its operations, adding a new production line.
Mrs Folorunsho Alakija, whose net worth dropped to $1.1 billion from $1.3 billion, was ranked 19th. She is vice chair, Famfa Oil, an indigenous oil exploration company with a stake in Agbami Oilfield, a prolific offshore asset. Famfa Oil's partners include Chevron and Petrobras.
Mrs. Alakija's first company was a fashion label, whose customers included former military President Ibrahim Babangida and his wife, the late Maryam.
The Federal Government awarded Mrs. Alakija's company an oil prospecting license in 1993, which was later converted to an oil mining lease.
Mrs. Alakija's ranking tied with South African banker, Michiel Le Roux.
Forbes blamed plunging stock values and weaker currencies for the shrinking in the billionaires club in Africa.
It said: "Buffeted by plunging stock prices and weaker currencies, the number of African billionaires has shrunk to just 20, down from 23 a year ago.
"Four people fell off Forbes' annual list of the continent's richest since last year while one returned to the ranks after a four-year absence. All but four members of the list have smaller fortunes than a year ago."
In a per country ranking, Egypt and South Africa are tied with five billionaires each, followed by Nigeria with four and Morocco-two.
Forbes found one billionaire each in Algeria, Angola, Tanzania and Zimbabwe.