Portuguese champions Porto have reached an agreement for the transfer of attacking midfielder Fabio Vieira to Premier League side Arsenal for 40 million euros ($42 million), the club announced on Friday.
Porto said Arsenal would pay an initial 35 million euros with a further five million dependent on the 22-year-old player achieving his targets at the English club.
The versatile Vieira, who has represented Portugal at the Under-21 level, scored seven goals and made 16 assists from 39 appearances in all competitions last season as Porto won the league and Cup double.
Vieira follows Brazilian forward Marquinhos and American goalkeeper Matt Turner in joining the club during the close season.
Arsenal finished fifth in the league last season and were beaten to the final automatic Champions League spot by north London rivals Tottenham Hotspur.