Chocobos can reach rank 10 simply by earning experience points.

However, to increase the maximum rank past 10, you must feed them Thavnairian onions. They may then earn further experience points and increase their rank up to the new maximum limit.

Read on for details regarding ranks 11 and above.

Chocobos can also earn experience points in chocobo stables built on free company or private housing estates. Other players may also leave their chocobo in your stable for training.

Please note that a chocobo's rank cannot increase while training in a stable. Once it has earned the required number of experience points, you must take it into combat to allow it to increase in rank.