This week, the Turkish Super Lig leader stated that a move for Arda was close to being finalised.
Barca announced that the 30 year-old will make the move on loan for the remainder of his contract.
LaLiga's leader also stated that it retains the right to sell Arda during this period, with Basaksehir holding an option to buy – although a price was not confirmed for this clause.
Arda opted to join Barca from LaLiga rival Atletico Madrid in July 2015, but a transfer ban imposed on the club meant he did not debut until the next January.
During his time at Camp Nou, Arda won medals in LaLiga, the Copa del Rey and the Supercopa de Espana, but failed to hit the same high standards he produced at Atleti.
Barca's club-record purchase of Philippe Coutinho further diminished his chances of regular first-team football and Arda opted for a return to Turkey, having previously won the domestic title in his home country during his time at Galatasaray.