Once an A-Support is achieved on two same sex characters (excluding Male Corrin and Niles and Female Corrin and Rhajat) one may further raise that bond to an A+ support to gain a new class. Every unit, except for the Avatar, can have only one A+ Support per playthrough. If the selected friend has a special base class such as Nohr Prince, Songstress, Kitsune, Wolfskin, or Villager, the secondary class will be adopted instead. Two units sharing a base class (Kaze and Saizo) instead receive the secondary class.
The Avatar cannot A+ any unit and cannot be used as an A+ Support. Instead though, they can still use the Friendship Seal once they have obtained an A-Support with any same sex unit to change into their base class.
Unlike S-Supports and the Partner Seal, the A+ rank support is non-reciprocal, meaning that the A+ support is one-sided for a particular character. For example, the player can have Hana A+ support with Felicia to obtain the Troubadour class with a Friendship Seal while Felicia A+ Supports her sister to obtain the the Dark Mage class.
- Scenario 1: - If Xander and Ryoma achieve an A+ Support, Xander will gain the Samurai class while Ryoma will gain the Cavalier class.
- Scenario 2: - If Camilla and Beruka achieve an A+ Support, Camilla will gain Beruka's secondary class of Fighter while Beruka gains Camilla's secondary class of Dark Mage.
- Scenario 3: - If Silas and Jakob achieve an A+ Support, Silas will gain access to the Troubadour class, while Jakob will gain nothing, since his secondary class is the Cavalier class.
- Scenario 4: - If Kaden and Keaton achieve an A+ Support, Kaden will gain access to the the Fighter class instead of the Wolfskin class while Keaton will gain access to the Diviner class instead of the Kitsune class.
- Scenario 5: - If Arthur and Keaton achieve an A+ Support, Arthur will gain access to the Outlaw class instead of the Fighter class while Keaton will gain nothing, since his secondary class is the Fighter class.