The Steam version of Five Nights at Freddy's 3 does not have any obtainable achievements.
However, these achievements are official and are included in the console ports of the game.
That being said, feel completely free to try and get all of these achievements just for funsies!
This guide also contains some SPOILERS for the game, you have been warned!

“Survived the 1st night.”
Beat Night 1.

“Survived the 2nd night.”
Beat Night 2.

“Survived the 3rd night.”
Beat Night 3.

“Survived the 4th night.”
Beat Night 4.

“Survived the 5th night.”
Beat Night 5.

“Survived nightmare mode.”
Beat Night 6.

“Finished your first week's shift.”
Beat the five nights.

“Got the good ending.”
Complete the secret minigames and get the Good Ending.


Step 1 - On Night 1/2, go to CAM 08 and double click BB's poster, go through the top left side of the screen, then wait until you fall and go right to get the balloon.
Step 2 - On Night 2, go to CAM 07 and press the arcade's buttons in the order Top Left Bottom Left Top Right Bottom Right, go through the top right side of the screen, then wait until you fall and go left to get the cake.
Step 3 - On Night 2, go to CAM 08 and double click BB's poster, go through the top left side of the screen, then wait until you fall and jump across the balloons to give the child a cake.
Step 4 - On Night 3, go to CAM 02, 03, 04, 06 and click the Shadow Cupcake on each camera, go down and go through the top left side of the screen, then give the child a cake.
Step 5 - On Night 4, find the 3x3 grid of tiles in your office that you can click and enter the code 395248 like in a numeric keypad, glitch through various places without entering the exit door to eventually find the child and give them a cake.
Step 6 - On Night 5, find the Shadow Bonnie figure on your office desk and click it, press S to change the map to find the BB's Air Adventure map and go through the top left side of the screen, then press S again to eventually find the child and give them a cake.
Step 7 - On Night 5, go to CAM 03 and double click Puppet's poster, go right and witness their Happiest Day, then beat Night 5.

“Survived aggressive nightmare mode.”
Beat Night 6 with the Aggressive cheat enabled.

“Failed to make it through the night.”
Get jumpscared by Springtrap.