Access Bank said both banks would operate under the new Access Bank brand from April 1.
In December, Access had agreed to buy mid-tier lender Diamond Bank with cash and shares, creating a bank with 29 million customers, which the two banks have said is more than any other bank in Africa.
The takeover will reduce the number of players in banking in Nigeria, where the top five banks control more than 60 percent of assets.
Diamond Bank shareholders also approved the takeover on Tuesday.
“Following receipt of regulatory approvals, the merger between Access Bank and Diamond Bank will proceed as planned. At this stage we expect to launch the new enlarged Access brand on April 1st,” the banks said in a statement.
Access agreed to the takeover after Diamond Bank had struggled since 2016 to bolster its capital following loan losses which had forced the bank to sell its foreign subsidiaries.
U.S. private equity firm Carlyle is one of the main shareholders in Diamond Bank, which has a strong focus on banking for retail customers and small businesses.
Shares in Diamond Bank closed flat on Tuesday at 2.50 naira each while Access Bank rose 0.84 percent.
