London's Metropolitan Police said a jury at Blackfriars Crown Court convicted 28-year-old Hasan Aydemir of sending the hoax bomb.
Prosecutors said he sent a parcel through a London branch of UPS in March 2011, telling staff it contained a teddy bear and a watch as wedding gifts for his sister.
He attached a note instructing "leave the package on the table of the bride and groom," and prosecutors said he later phoned the reception hall in the Istanbul district of Gungoren, to make sure the instructions would be carried out.
A customs officer at Ataturk Airport in Istanbul found the package contained a device made from a clock, wires and putty. Bomb-disposal experts were called and declared the item a hoax.
Aydemir, who was arrested at his home in London six days after sending the package, pleaded not guilty. But the jury decided he had sent the device while involved in a family dispute about his sister's wedding.
British police counterterrorism coordinator Stuart Osborne said Aydemir's actions "were extremely irresponsible and wasted valuable police resources both in Turkey and in London."