February 24, 2005 - ENM quests are added. Each ENM battlefield can be challenged every five days simply by obtaining a key item. Rewards include rare materials and gear with high stats.

February 24, 2005 - The southern half of Al'Taieu is released along with the eighth chapter of Chains of Promathia. The northern half is later added in October along with Limbus. Al'Taieu is commonly referred to as the "sea," based on the area's environment and monsters.

February 24, 2005 - The fishing system is changed, and catching a fish now requires moving the rod as directed to lower the fish's HP. Prior to this, fishing only required the press of a button.

Diorama Abdhaljis-Ghelsba is added for private Ballista matches. Since it can be reserved for private use, the area also doubles as a venue for player events.

July 19, 2005 - Chains of Promathia concludes with the ending theme "Distant Worlds" performed by Izumi Masuda. This is the first time a song with vocals is played in-game, as well as the first time an ending is unobstructed by UI elements.

July 18, 2005 - Lost chocobo quests begin appearing in chocobo stables in the three nations and Kazham. Miratete's Memoirs and other rewards can be obtained by completing these quests quickly.

July 19, 2005 - A number of rewards are changed for Orb Battles are changed. Peacock Charm, previously obtained from the NM Argus in the Maze of Shakhrami, particularly skyrockets in demand, leading to an increase in feuds and market prices. This leads to the NM drop being switched to the Peacock Amulet with identical effects, and the Peacock Charm becoming a battle reward from the Orb Battle "Under Observation."

July 19, 2005 - The Fellowship system and Fellowship quests are added, allowing players to call adventuring fellow NPCs to their side. Adventuring fellows gain levels as you fight alongside them, and require completing the Limit Break quests to raise their level cap above 50.

A stronger version of weakness status, commonly referred to by players as “double weakness,” is added. This is inflicted upon resurrected players who were already afflicted with weakness status prior to being K.O.’d, and lowers the accuracy and damage of their magical and ranged attacks to their lowest possible state. This addition of double weakness prevents the use of “zombie strategies” where players chip away at an enemy with magical attacks while repeatedly getting K.O.’d and resurrected.

July 22, 2005 - Beginning this year, the summer festival event from the previous year is held as the Sunbreeze Festival. The Azimuth Circle mini game is added, which rewarded swimsuits.

SQUARE ENIX PARTY 2005, an official event celebrating all things Square Enix, is held at the Makuhari Messe in Chiba, Japan. The FFXI booth hosts a special battlefield known as Heroes Combat, where adventurers are pit against some of Vana’diel’s greatest champions: Trion, Volker, and Ajido-Marujido.

August 24, 2005 - THE STAR ONIONS, a band formed around Naoshi Mizuta and Kumi Tanioka, releases their first album. THE STAR ONIONS performed at various FINAL FANTASY XI events between 2004 and 2007.

Blitz Buffalo, an official event themed after the Spanish tradition of the Running of the Bulls, is held, where participants can obtain the Red Sash and Dash Sash by defeating the Buffalo NMs Toro and Miura. Though Blitz Buffalo does not return in the following years, the event is reintroduced in 2008 as Blazing Buffalo, where the objective is to guide Buffaloes rather than cull them. (Photo from Blazing Buffalo.)

October 11, 2005 - Limbus, content to be undertaken with an alliance, is added. It is largely divided into the Apollyon and Temenos areas. Ancient beastcoins obtained in these areas can be exchanged for various rewards or used to upgrade artifact gear. Additionally, rewards from certain areas can be exchanged for Homam gear and Nashira gear.

December 13, 2005 - Dynamis-Valkurm, Dynamis-Buburimu, and Dynamis-Qufim are added. Completion of these three areas unlocks Dynamis-Tavnazia, added in February of the following year.

December 13, 2005 - The quest "Storms of Fate" is added as an afterstory to the events of Chains of Promathia. Completing the quest allows adventurers to challenge the more difficult "The Wyrmking Descends."

December 13, 2005 - The quest "Waking Dreams," is added, enabling players to form a pact with Diabolos.

December 13, 2005 - Dragoon's original SP ability, Call Wyvern, is changed into a regular ability with its recast time and effects adjusted. Spirit Surge, a new ability in which the dragoon calls upon the wyvern's strength, takes its place as their new SP ability.

Monster behaviors are adjusted as a countermeasure against monster player killing (MPK). As a result of the change, if the players targeted by a monster are K.O.’d or change areas while outside of the monster’s designated spawn point, the monster will disappear and immediately respawn in its spawn point.