BA described the Iranian capital as “an important destination” for the airline.
The resumption of flights on Thursday follows the lifting of some sanctions against Iran in January after the international nuclear watchdog said the Tehran government had met all its obligations under a deal with six world powers.
The then-foreign secretary Philip Hammond said at the time that British firms should take advantage of the new opportunities that would open as Iran was brought in from the cold.
In August last year the British embassy in Tehran reopened after it was ransacked by a mob in 2011.
The first BA flight to Iran, a Boeing 777, will depart from Heathrow Terminal 5 on Thursday at 9.10pm.
Flights were initially due to resume in July but there was a delay in establishing the route.
Sean Doyle, BA's head of network and fleet, said: “British Airways has a long history of flying to Iran so we are very excited to be launching our new six-times-a-week service, direct from Heathrow to Tehran.
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“Iran is a fascinating country, full of amazing and surprising places for tourists to visit and discover its sophisticated and ancient culture.
“The recent lifting of sanctions has also effectively allowed Iran to re-open for business and paved the way for commerce to reconnect with Iran's economy, which is the second largest in the Middle East and North Africa, with a diverse range of businesses and industries.”
Air France resumed Paris-Tehran flights in April for the first time in eight years.
Press Association
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