And he insisted the costs of his new government would not be as high as people might think.
"The number, for instance, among the deputy ministers — 42 out of 50 are all parliamentarians, and in effect converting them from parliamentarians into ministers, the marginal cost of that transformation is minimal in terms of the public exchequer," he said.
The ministers are needed for the "rapid transformation of this country", Akufo-Addo said.
George Lawson, deputy general secretary of the opposition National Democratic Congress (NDC), told AFP that the increase in the number of ministers was "not proper" and charged that Akufo-Addo was giving out "jobs for the boys".
"It's a drain on the Ghanaian economy," he added.
Akufo-Addo came to power in January after beating the NDC's John Dramani Mahama in December's election.
The new president says he has inherited an economy reeling from huge fiscal deficits, rising inflation and high unemployment despite an IMF programme designed to stimulate growth.