Is there a FedEx office in the Tianjin airport?

There is FedEx office in the airport.

Thank you Abbey. Can you describe where it is from international departures

According to the information on the offcial website of FedEx, there is no their office in TJ airport, so I think Abbey may make a small mistake.
If you want to deliver an international parcel, you can call 800 988 1888 to ask where you can send it. If you want to deliver the domestic parcel, you can call 400 889 1888 to ask the place.