| Kozmo SoartroopersBreakers of Shadow · 083 | Breakers of Shadow | 083 | Super Rare | €0.30 |
| Kozmo StrawmanDimension of Chaos · 082 | Dimension of Chaos | 082 | Ultra Rare | €2.14 |
| Kozmo TincanBreakers of Shadow · 082 | Breakers of Shadow | 082 | Ultra Rare | €0.39 |
| KozmotownClash of Rebellions · 086 | Clash of Rebellions | 086 | Rare | €0.15 |
| KozmourningShining Victories · 086 | Shining Victories | 086 | Common | €0.05 |
| Krawler AxonCircuit Break · 017 | Circuit Break | 017 | Common | €0.07 |
| Krawler DendriteCircuit Break · 021 | Circuit Break | 021 | Common | €0.09 |
| Krawler GlialCircuit Break · 018 | Circuit Break | 018 | Common | €0.05 |
| Krawler RanvierCircuit Break · 020 | Circuit Break | 020 | Common | €0.02 |
| Krawler ReceptorCircuit Break · 019 | Circuit Break | 019 | Common | $0.05 |
| Krawler SomaPower of the Elements · 029 | Power of the Elements | 029 | Common | €0.09 |
| Krawler SpineCircuit Break · 016 | Circuit Break | 016 | Common | €0.09 |
| KrebonsThe Duelist Genesis · 018 | The Duelist Genesis | 018 | Common | €0.25 |
| Krishnerd WitchLegacy of Destruction · 084 | Legacy of Destruction | 084 | Common | €0.12 |
| KrokodilusUnlisted Printings | Unlisted Printings | — | — | — |
| Krystal AvatarYu-Gi-Oh! The Dark Side of Dimensions Movie Pack · 011 | Yu-Gi-Oh! The Dark Side of Dimensions Movie Pack | 011 | Ultra Rare | $0.13 |
| Krystal DragonYu-Gi-Oh! The Dark Side of Dimensions Movie Pack: Gold Edition · 2 | Yu-Gi-Oh! The Dark Side of Dimensions Movie Pack: Gold Edition | 2 | Gold Secret Rare | €0.21 |
| KryuelPharaonic Guardian · 006 | Pharaonic Guardian | 006 | Common | $0.19 |
| KuebikoThe Infinite Forbidden · 083 | The Infinite Forbidden | 083 | Super Rare | €0.02 |
| Kuibelt the Blade DragonDuelist Nexus · 083 | Duelist Nexus | 083 | Common | €0.13 |
| KujakujakuJudgment of the Light · 098 | Judgment of the Light | 098 | Common | €0.08 |
| Kuji-Kiri CurseIgnition Assault · 066 | Ignition Assault | 066 | Super Rare | €0.09 |
| Kumenyo, the Nine-Hued DeerBeyond the Brave · 084 | Beyond the Brave | 084 | Common | €0.08 |
| Kumongous, the Sticky String KaijuClash of Rebellions · 088 | Clash of Rebellions | 088 | Rare | €0.16 |
| KumootokoLegend of Blue Eyes White Dragon · 082 | Legend of Blue Eyes White Dragon | 082 | Common | €0.02 |
| Kunai with ChainThe Duelist Genesis · 098 | The Duelist Genesis | 098 | Super Rare | €0.06 |
| KunoichiThe Duelist Genesis · 031 | The Duelist Genesis | 031 | Common | €0.04 |
| KuramaLegend of Blue Eyes White Dragon · 039 | Legend of Blue Eyes White Dragon | 039 | Common | €0.02 |
| Kuraz the Light MonarchLight of Destruction: Special Edition · 1 | Light of Destruction: Special Edition | 1 | Super Rare | €0.50 |
| KuribabylonBrothers of Legend · 005 | Brothers of Legend | 005 | Ultra Rare | €0.24 |
| KuribahBrothers of Legend · 001 | Brothers of Legend | 001 | Ultra Rare | €0.19 |
| KuribanditDragons of Legend · 002 | Dragons of Legend | 002 | Secret Rare | €0.06 |
| KuribeeBrothers of Legend · 002 | Brothers of Legend | 002 | Ultra Rare | €0.19 |
| KuribehBrothers of Legend · 004 | Brothers of Legend | 004 | Ultra Rare | €0.26 |
| KuribohMetal Raiders · 071 | Metal Raiders | 071 | Super Rare | €0.05 |
| Kuriboh - Multiply!Magnificent Monsters · 002 | Magnificent Monsters | 002 | Grand Master Rare | €3.33 |
| KuribohrnStructure Deck: Yugi Muto · 005 | Structure Deck: Yugi Muto | 005 | Common | €0.15 |
| Kuriboh TokenYu-Gi-Oh! Advent Calendar (2019) · 003 | Yu-Gi-Oh! Advent Calendar (2019) | 003 | Super Rare | €0.37 |
| KuribonAncient Prophecy · 001 | Ancient Prophecy | 001 | Rare | €0.07 |
| Kuribon the Fairy SpiritAlliance Insight · 008 | Alliance Insight | 008 | Common | €0.02 |
| KuribooBrothers of Legend · 003 | Brothers of Legend | 003 | Ultra Rare | €0.16 |
| Kurikara DivincarnatePower of the Elements · 031 | Power of the Elements | 031 | Secret Rare | $6.83 |
| Kurikurinku @IgnisterAlliance Insight · 003 | Alliance Insight | 003 | Common | €0.05 |
| KuriphotonZexal Collection Tin · 009 | Zexal Collection Tin | 009 | Ultra Rare | €0.25 |
| KurivoltOrder of Chaos · 001 | Order of Chaos | 001 | Common | €0.09 |
| Kuro-Obi Karate SpiritExtreme Force · 081 | Extreme Force | 081 | Common | €0.06 |
| Kuwagata αTournament Pack: 1st Season · 030 | Tournament Pack: 1st Season | 030 | Common | $0.12 |
| Kuzuha the Hex AshtraBeyond the Brave · 010 | Beyond the Brave | 010 | Common | €0.10 |
| Kwagar HerculesTournament Pack: 1st Season · 003 | Tournament Pack: 1st Season | 003 | Super Rare | €0.02 |
| Kycoo the Ghost DestroyerLabyrinth of Nightmare · 062 | Labyrinth of Nightmare | 062 | Super Rare | €0.94 |