"The impact of the cyberattack on TNT Express and lower-than-expected results at FedEx Ground reduced our first quarter earnings," said Alan Graf, FedEx chief financial officer. "We are currently executing plans to mitigate the full-year impact of these issues."
Combed with the impact of Hurricaine Harvey, the cyber attack "posed significant operational challenges" said Fred Smith, FedEx chairman and chief executive officer.
While no data breach or data loss occurred as a result of Petya, the company previously warned that it may not be able to recover all of the systems affected by the cyber attack.
"The worldwide operations of TNT Express were significantly affected during the first quarter by the June 27 NotPetya cyberattack. Most TNT Express services resumed during the quarter and substantially all TNT Express critical operational systems have been restored. However, TNT Express volume, revenue and profit still remain below previous levels," the company said.
FedEx was one of a number of high-profile victims of the Petya malware epidemic, which originated in Ukraine but spread to bring down IT systems around the world.
Reckitt Benckiser -- the company behind Dettol cleaning products, the Nurofen painkiller, Durex condoms and more -- has also predicted £100m in lost revenue as a result of falling victim to the attack.