The Competition and Markets Authority announced its investigation into the £11bn (€12.7bn, $13.5bn) deal on Monday.
Standard Life said it put the deal forward for investigation itself as an “expected” part of the merger process.
If finalised, the merger would mean the renamed Standard Life Aberdeen would become one of the largest fund managers in the world, overseeing assets worth £660bn.
An initial decision on whether to take the investigation further will be made by 18 July this year.
In a statement, the watchdog said its investigation would examine “whether the creation of that situation may be expected to result in a substantial lessening of competition within any market or markets in the United Kingdom for goods or services”.
The two firms were forced to confirm they were in merger talks in early March, in a move that saw shares sky-rocket in the days following the announcement.
In the weeks that have followed the two firms have revealed how the board will look and that around 800 jobs will be lost as a result of the deal.
Aberdeen’s head of UK distribution Martyn Gilbey has also announced he will leave to join Franklin Templeton.
In a statement, Standard Life said: “Standard Life today filed an application with the CMA in respect of the proposed merger with Aberdeen Asset Management.
“This has triggered the CMA’s standard phase one review of this application. This is one of a number of regulatory approvals being sought as part of the merger process.”
