The former Lille defender completing a reported £22 million ($30 million) move from Lille on Tuesday.
The 22-year-old defender was also in demand from Manchester United and Napoli after impressing as Lille finished fourth in the curtailed 2019/20 Ligue 1 season.
Gabriel adds to Arsenal’s growing Brazilian contingent since the club’s former midfielder Edu left his role as coordinator for the Brazilian national team to become technical director last year.
Arteta, who has guided the Gunners to the FA Cup and Community Shield in his first nine months in charge, also helped swing Gabriel’s final decision.
“Edu and I had several chats about Arsenal and the new project, we had many good conversations,” Gabriel told Arsenal Digital.
“As the days went by I was getting very excited about it, then I had a call from the coach and that was very reassuring.
“Having the coach himself calling you to say he wants you in his squad motivates you a lot. That is the very reason I am here today.
“We did not talk about (details), he just told me he is aware of my quality, my capacity and how far I can go. He also said he will be very demanding with me.”
Despite their cup success, Arteta was looking for defensive reinforcements after finishing eighth in the Premier League last season — Arsenal’s lowest league finish since 1994/95.
“He has many qualities which will make us stronger as a defensive unit and as a team,” said Arteta. “He has proved with Lille that he is a defender with many outstanding attributes and we are looking forward to watching him grow as an Arsenal player.”
Gabriel joins experienced Brazilian international duo David Luiz and Willian, who is Arsenal’s only other signing so far in the close season.
“He is a player we have been studying for a while and he was in demand from many clubs, so we are proud to have agreed and completed this transfer with Lille and the player,” said Edu.
“Gabriel is a player of high quality and Mikel and his coaches are looking forward to integrating him into the club.”
Arsenal are also reportedly close to agreeing another season-long loan deal for Dani Ceballos from Real Madrid, while Arteta said after Saturday’s Community Shield victory over Liverpool that club captain Pierre-Emerick Aubameyang is close to extending his contract to remain at the Emirates.