Significant events that happened in 2015
January
- 1 - The first wave of 2015 LEGO Ninjago sets were officially released in Europe.
- 20 - LEGO Ninjago: Masters of Spinjitzu Season 3 volume 2 was released on DVD in the United States.
- 27 - The Tournament of Elements was released.
February
- 23 - Season four episodes "The Invitation" and "Only One Can Remain" aired in the United States.
- 24 - The Search for Zane and The Rescue Mission were released.
March
- 1 - The first wave of 2015 LEGO Ninjago sets were officially released in the United States.
- 9 - Season four episode "Versus" aired in the United States.
- 16 - Season four episode "Ninja Roll" aired in the United States.
- 23 - Season four episode "Spy for a Spy" aired in the United States.
- 30 - Season four episode "Spellbound" aired in the United States.
- 31 - Season four episode "The Forgotten Element" aired in the United States.
April
- 1 - Season four episode "The Day of the Dragon" aired in the United States.
- 2 - Season four episode "The Greatest Fear of All" aired in the United States.
- 3 - Season four finale "The Corridor of Elders" aired in the United States.
- 28 - Ninja vs. Ninja and Breakout! were released.
May
- Unknown - The second wave of 2015 LEGO Ninjago sets and Airjitzu Flyers were officially released in Europe.
June
- 16 - LEGO Ninjago: Secret World of the Ninja was released.
- 29 - Season five episode and premiere "Winds of Change" aired in the United States.
- 30 - Season five episode "Ghost Story" aired in the United States.
July
- 1 - Season five episode "Stiix and Stones" aired in the United States.
- 2 - Season five episode "The Temple on Haunted Hill" aired in the United States.
- 3 - Season five episode "Peak-a-Boo" aired in the United States.
- 6 - Season five episode "Kingdom Come" aired in the United States.
- 7 - Season five episode "The Crooked Path" aired in the United States.
- 8 - Season five episode "Grave Danger" aired in the United States.
- 9 - Season five episode "Curseworld, Part I" aired in the United States.
- 10 - Season five episode and finale "Curseworld, Part II" aired in the United States.
- 28 - Spy vs. Spy was released.
August
- 1 - The second wave of 2015 LEGO Ninjago sets and Airjitzu Flyers were officially released in the United States.
- 25 - World of Ninjago was released.
September
- 29 - The Way of the Ghost's was released.
December
- 29 - Attack of the Sky Pirates was released.