The centre-back, who spent three years at Manchester City, will originally arrive on loan with an option to buy in the summer window
Arsenal are finally set to land Pablo Mari after a deal was agreed with Flamengo for the Spanish defender.
Mari flew to England alongside Arsenal technical director Edu on Saturday to undergo a medical but returned to Brazil on Sunday after the clubs failed to agree on the terms of his move.
Negotiations have continued, however, and there was a breakthrough overnight with Mari given permission by Flamengo to return to London to finalise his switch to Emirates Stadium.
Sources in Brazil suggest Arsenal have agreed to pay a loan fee of £4.25m to secure Mari, who spent three seasons as a Manchester City player between 2016 and 2019, until the end of the 2019-20 campaign.
The news will come as a boost to Mikel Arteta, who has seen his options at centre-back limited since Calum Chambers was ruled out for nine months after rupturing the cruciate ligament in his knee.
There were also fears that Shkodran Mustafi would join Chambers on the long-term absentee list when he was stretchered off with an ankle injury, having clashed with goalkeeper Emiliano Martinez during Monday night’s FA Cup win at Bournemouth.
“We will have to assess him but when Mustafi has to come off, normally it is not good,” Arteta told BBC Sport after the match.
“We are in the market. We are looking for some things with the resources we have and we will tell you when we have more news.”
However, scans have shown the German World Cup winner only suffered a sprain and that he could be back after the mid-season break when Arsenal host Newcastle United.
The Gunners travel to Burnley on Sunday in the Premier League but Mari is not expected to be involved at Turf Moor, even if his transfer is finalised in time.