In a message on Thursday, Iranian Foreign Ministry Spokesman Bahram Qassemi expressed sympathy with the American citizens affected by the disaster and with the bereaved families of the victims.
He also expressed regret at the damages and losses caused by the tropical storm and flooding that have hit parts of the United States.
Since coming ashore on August 25, heavy rains from Hurricane Harvey have claimed the lives of dozens of people and sent more than 32,000 to shelters south of the US.
The tropical storm made a second landfall in the state of Louisiana as large parts of Texas remain under water following record rainfall that forced tens of thousands of people from their homes.