- Given to the Dragonborn by Tonilia if they become a member of the Thieves Guild.
- Another full set can be found in the training room area of the guild. It rests on the tables and cupboards of the Ragged Flagon - Cistern and respawns eventually.
- An additional armor piece can be located in the room with the practice locked chests, on the top of the right hand side cupboard in the Cistern.
Thieves Guild Armor can be upgraded at a workbench with Leather and the Arcane Blacksmith perk; however, it does not benefit from any Smithing perks. This means the armor cannot be improved past flawless quality without boosting the Smithing skill over 100. This can be achieved by using enchanted items and/or blacksmithing potions to fortify Smithing.
Wearing this piece of armor grants the following skill bonuses:
- Fortify Carry Weight: 20 points
After completing the quest "Scoundrel's Folly" without killing Gulum-Ei, the opportunity for Tonilia to upgrade one piece of the armor opens up. Upgrading the cuirass increases the Fortify Carry Weight enchantment to 35 points.
After completing the quest "Under New Management", the current set of Thieves Guild Armor is exchanged for a superior set called the Guild Master's Armor. The Guild Master's Armor has an improved Fortify Carry Weight enchantment even stronger than an upgraded Thieves Guild Armor.