The Gunners have agreed a deal with Barcelona for the 23-year-old, who wanted to leave in search of more first-team football.
Codina will join off the back of winning the Women’s World Cup with Spain, who defeated England 1-0 in the final on Sydney.
She was a regular for Spain during the tournament, taking the place of Mapi Leon, who has been on strike from the national team since September last year.
Codina will be the second centre-back Arsenal have signed this summer after they also brought in Amanda Ilestedt.
The 30-year-old was a free agent after her contract expired at Paris-Saint Germain. She enjoyed an excellent World Cup, scoring four goals as Sweden finished third.
Arsenal have made adding strength to their defence a priority after Brazil captain Rafaelle Souza left for Orlando Pride.
