The probe is being undertaken by NYSE Regulation which is scrutinising the Dutch bank over the fact that the volume of share trading in ABN Amro was significantly higher than normal on some days in March.
On March 12th, some 2.68 million shares were traded in ABN Amro, while on March 15th, the figure stood at 1.05 million.
However, on average the amount of ABN Amro shares changing hands daily is just 513,000.
A spokesman for ABN Amro said: "We have received an inquiry from the NYSE. They have started an inquiry into the trading of our shares. The inquiry is being conducted as part of the NYSE's policy of investigating market activity around corporate announcements. We're fully cooperating."
Barclays is vying with a Royal Bank of Scotland-led consortium to acquire the Amsterdam-based bank.