It said it bought the two unnamed 2005-built ships for $36.5m each. The ships are due to be handed over by August.
The US-listed suezmax specialist said the acquisitions will be financed from the financial resources of the company.
In April NAT raised net proceeds of over $113m from the sale of 13.8m of its shares in a public offering.
The Herbjorn Hansson-led company says the latest acquisitions increase the NAT fleet to 22 suezmax vessels.
“The