Here is the full list of all 37 Thief achievements. It takes around 40-50 hours to unlock all of the achievements on Windows.
Finished Chapter One
Uncovered Lyegrove's secret
Finished the Prologue
Stole all loot and collectibles in a single chapter.
Picked 100 pockets in a single playthrough
Picked a lock with masterful speed
Finished the game with a custom difficulty of 700 points or more
Completed 10 optional Thieving Objectives
Completed 25 optional Thieving Objectives
Finished 3 consecutive chapters without taking damage
Picked a pocket and a lock using the focus ability
Finished the game without a single kill or knockout
Disarmed ten trap mechanisms
Reached the final chapter without using the focus ability
Finished the game on Master difficulty
Scored an epic 5,000,000 or more in a Challenge Map
Finished a single chapter without alerting anyone
Shot a bottle in mid-air with an arrow
Killed or knocked out 10 people using the environment
Completed a collectible set
Completed all collectible sets
Sweet sixteen. Snuff said.
Discovered 15 secret areas
Discovered all secret areas
Used 40,000 gold
Completed all client jobs in The City
Completed all Basso Jobs in The City
Stole 5 collectibles
Found all the secret stashes in Moira
Finished Chapter Two
Finished Chapter Three
Finished Chapter Four
Finished Chapter Five
Finished Chapter Six
Finished Chapter Seven
Finished Chapter Eight
Finished the game in 15 hours or more