| One Piece - Pirate Warriors | 2012 | ps3 |
| OneShot: World Machine Edition | 2022 | switch |
| Onigokko! Portable | 2013 | psp |
| Only You - Rebel Cross | 2003 | ps2 |
| Ookami to Koushinryou - Boku to Holo no Ichinen | 2008 | nds |
| Ookami to Koushinryou - Umi o Wataru Kaze | 2009 | nds |
| Oookuki | 2008 | ps2 |
| Oozy the Goo Slime Quest | 2022 | a2600 |
| Open Roads | | ps4 |
| Or Maybe This Is the Perfect Life | 2025 | genesis |
| Or Maybe This Is the Perfect Life - The Harry Fox Story | 2026 | genesis |
| Oracle no Houseki - Jewels of the Oracle | 1996 | ps1, saturn |
| Orange Honey - Boku wa Kimi ni Koi shiteru | 2007 | ps2 |
| Orange Pocket - Cornet | 2004 | dreamcast |
| Orange Pocket - Root | 2004 | ps2 |
| Ord. | 2020 | ps4, xboxone |
| Ore no Imouto ga Konna ni Kawaii Wake ga Nai - Portable ga Tsuzuku Wake ga Nai | 2012 | psp |
| Ore no Imouto ga Konna ni Kawaii wake ga Nai Portable | 2011 | psp |
| Ore no Kanojo no Uraomote - Pure Sweet Heart | 2013 | psp |
| Ore no Shita de Agake | 2007 | ps2 |
| Ore no Yome - Anata dake no Hanayome | 2010 | xbox360 |
| Ore wa Shoujo Mangaka | 2012 | psp |
| Oretachi ni Tsubasa wa Nai | 2014 | ps3, vita |
| Oretachi no Sekai wa Shimatteiru | 2017 | vita |
| Orfleurs - Koufuku no Hanataba | 2017 | vita |
| Oro e Gloria - La Strada per El Dorado | 2000 | ps1 |
| Oro y Gloria - La Ruta hacia El Dorado | 2000 | ps1 |
| Osawari Tantei Ozawa Rina Rising 3 Nameko wa Banana no Yume wo Miruka | 2014 | 3ds |
| Oshare Princess 3 | 2003 | gba |
| Oshare Princess 5 | 2005 | gba |
| Oshiete! Popotan | 2004 | ps2 |
| Osomatsu-kun - Back to the Me no Deppa no Maki | 1989 | nes |
| Osouji Sentai Clean Keeper | 2008 | wii |
| Otogirisou | 1992 | snes |
| Otoko Yuukaku | | vita |
| Otome no Jijou | 2006 | ps2 |
| Otome wa Boku ni Koishiteru | 2005 | ps2 |
| Otome wa Boku ni Koishiteru Portable - Futari no Elder | 2011 | psp |
| Otome wa Oanesama Boku ni Koi Shiteru Portable | 2010 | psp |
| Otome-teki Koi Kakumei - Love Revo!! DS | 2008 | nds |
| Otome-teki Koi Kakumei - Love Revo!! Portable | 2010 | psp |
| Otona no DS Mystery - Izumi Jiken File | 2004 | nds |
| Otoshi Deka - Keiji-san, Watashi ga Yarimashita | 2008 | nds |
| Ouka - Kokoro Kagayakaseru Sakura | 2006 | ps2 |
| Ouka Sabaki Zan | 2018 | vita |
| Ouka Sengoku Portable | 2012 | psp |
| Oumagatoki | 2001 | ps1 |
| Oumagatoki - Kaidan Romance | 2012 | psp |
| Oumagatoki 2 | 2001 | ps1 |
| Our World is Ended | 2019 | ps4, switch, xboxone |
| Ouran Koukou Host Club | 2007 | ps2 |
| Ouran Koukou Host Club DS | 2009 | nds |
| Oure | 2017 | ps4 |
| Out There: Ω The Alliance | 2019 | switch |
| Out of Galaxy - Gin no Koushika | 2009 | wii |
| Over Requiemz | 2025 | switch |
| Over the Hedge | 2006 | gba |
| Owaru Sekai to Birthday | 2017 | vita |
| Oxenfree | 2016 | ps4, switch, xboxone |
| Oxenfree II: Lost Signals | 2023 | ps4, switch |
| Oyako Entertainment Series - TV Kamishibai Vol. 1 | 1999 | ps1 |
| Oz no Mahoutsukai - Another World - Rung Rung | 2000 | ps1 |
| Ozmafia!! - Vivace | 2015 | vita |
| PC Engine Best Collection - Ginga Ojousama Densetsu Collection | 2008 | psp |
| PW - Project Witch | 2009 | psp |
| Pac-Man 2 - The New Adventures | 1994 | genesis, snes |
| Pac-Man 2 - The New Adventures | 2016 | wiiu |
| Paddington - Adventures in London | 2015 | 3ds |
| Pajama Sam - Don't Fear the Dark | 2008 | wii |
| Pajama Sam - You Are What You Eat from Your Head to Your Feet | 2001 | ps1 |
| Palais de Reine | 2010 | ps2 |
| Paleo Pines | 2023 | ps4, switch, xboxone |
| Pandora - Kimi no Namae o Boku wa Shiru | 2010 | ps2 |
| Pandora Max Series Vol. 2 - Shisha no Yobu Yakata | 2000 | ps1 |
| Pandora Max Series Vol. 4 - Catch! Kimochi Sensation | 2000 | ps1 |
| Pandora Max Series Vol. 5 - Gochachiru | 2000 | ps1 |
| Pandora no Yume | 2002 | dreamcast |
| Panic Palette | 2007 | ps2, psp, vita |
| Panic-chan | 1997 | saturn |
| Pantsu Hunter - Back to the 90s | 2019 | vita |
| Paper Beast | 2020 | ps4 |
| Paper Mario - Sticker Star | 2012 | 3ds |
| Papetura | 2022 | switch |
| Papo & Yo | 2012 | ps3 |
| Paradigm Paradox | 2021 | switch |
| Paradise Lost | 2021 | ps4, xboxone |
| Parascientific Escape Cruise in the Distant Seas | 2016 | 3ds |
| Parfait | 2015 | vita |
| Parfait - Chocolat Second Style | 2006 | ps2 |
| Parfait Remake | 2021 | ps4, switch |
| The Park | 2016 | ps4, switch, xboxone |
| Passing Breeze - An Arcade Adventure | 2022 | genesis |
| Pastel Chime Continue | 2010 | psp |
| Pastel Lime | 1992 | pcengine |
| Path of Mystery: A Brush with Death | 2024 | switch |
| Path of Sin: Greed | 2019 | ps4, xboxone |
| Patissier na Nyanko - Hatsukoi wa Ichigo Aji | 2004 | dreamcast |
| Patissier na Nyanko - Hatsukoi wa Ichigo Aji | 2004 | ps2 |
| Patito Feo | 2010 | psp |
| Patlabor - Chapter of Griffon | 1993 | pcengine |