| Safari Games | — | 2 | — |
| Saga Planets | — | 5 | 4 |
| Sakata SAS Co., Ltd. | 1985 | 2 | — |
| Sammy Corporation | November 1975 | — | 12 |
| Sandlot | March 12, 2001 | 7 | — |
| Sanrio | August 10, 1960 | 2 | — |
| Sanritsu Denki | — | 2 | — |
| Santa Entertainment | 1997 | 1 | — |
| Sanyo | February 1947 | 1 | — |
| SAT-BOX | — | 3 | 3 |
| Scitron & Art Inc. | 1988 | 2 | — |
| Sega AM2 | October 1983 | 31 | — |
| Sega Amusement | November 26, 1971 | 1 | — |
| Sega Fave | April 1998 | — | 1 |
| Sega Interactive | April 2015 | 1 | 3 |
| Sega Sammy Holdings | October 2004 | — | 3 |
| Sega Sports R&D | 1994 | 12 | — |
| Sega Wow | 2003 | 18 | — |
| Seibu Kaihatsu | 1982 | 8 | 5 |
| SETA Corporation | October 1985 | 3 | — |
| Shall Luck Plus | 2002 | — | 1 |
| Shift | June 1999 | 3 | — |
| Shiravune | 2019 | — | 16 |
| Shochiku | 1895 | — | 1 |
| Shoeisha | 2006 | — | 1 |
| Shogakukan-Shueisha Productions | June 26, 1967 | 1 | 2 |
| Shueisha Games | February 16, 2022 | — | 2 |
| Siesta | — | 1 | 1 |
| Silicon Studio | November 22, 1999 | 3 | — |
| Silky's | — | 4 | 4 |
| Silver Bullet | — | — | 1 |
| SilverStarJapan Co., Ltd. | June 11, 1997 | — | — |
| SIMS Co., Ltd. | June 12, 1991 | 6 | 1 |
| SITER SKAIN | — | 2 | — |
| Skeleton Crew Studio | — | 1 | — |
| Skip Ltd. | July 2000 | 10 | — |
| Skipmore | — | 1 | — |
| SMEE | — | 1 | 1 |
| SmileBoom | January 15, 2008 | 1 | 1 |
| SNK | December 2016 | 55 | 51 |
| SNK | April 1986 | 17 | 38 |
| Softhouse Chara | 2000 | 8 | 8 |
| Softhouse-seal | 2009 | 1 | 2 |
| Soleil | August 2008 | 2 | — |
| Sonic Powered | April 1998 | 2 | — |
| Sonic Team | 2000 | 74 | — |
| Sony | April 2021 | — | 1 |
| Sony Group | May 7, 1946 | 1 | 3 |
| Sony Music Entertainment Japan | March 11, 1968 | — | 3 |
| Sony Network Communications Inc. | November 1995 | — | 1 |
| Sonzai Games | — | 1 | — |
| Sora Ltd. | 2005 | 5 | — |
| SORAYUME | September 21, 2005 | 1 | 1 |
| Spike | 2005 | 15 | 16 |
| Spike Chunsoft | 2012 | 21 | 27 |
| Square | September 1986 | 39 | 42 |
| Square Enix | 1975 | 107 | 243 |
| Square Enix Business Division 1 | December 2013 | 1 | — |
| St.GIGA | 1990 | — | 3 |
| STARFISH-SD | 1994 | 1 | 3 |
| Sting | February 7, 1989 | 17 | 4 |
| Straight Edge | April 2016 | — | — |
| Studio e.go! | 1998 | 14 | 10 |
| Studio Line | August 1997 | 1 | — |
| Studio Mebius | — | 2 | 2 |
| Studio Nue | 1972 | — | — |
| Studio Ryokucha | 2001 | 1 | 1 |
| Studio Saizensen | — | 7 | — |
| Success | 1978 | 14 | 11 |
| Sumzap | — | 1 | 1 |
| Sunrise Interactive | 1998 | 2 | — |
| Sunsoft | 1978 | 17 | 26 |
| Suzak Inc. | June 26, 2000 | 4 | — |
| Swan | October 5, 1995 | 7 | 7 |
| Syn Sophia | 1995 | 15 | — |
| System Sacom | 1981 | 4 | 1 |
| SystemSoft | September 28, 1979 | 1 | 1 |
| SystemSoft Alpha | April 1999 | 1 | 7 |
| T-ARTS | February 9, 1988 | — | 2 |
| Tactics | 1997 | 1 | — |
| Taito | August 24, 1953 | 61 | 86 |
| Takara | September 17, 1955 | 3 | 24 |
| Takeru | — | 1 | 1 |
| Takumi Corporation | 1994 | 4 | — |
| Takuyo | February 1991 | 7 | 7 |
| Tamsoft | June 26, 1992 | 35 | — |
| Tango Gameworks | March 2010 | 4 | — |
| Tasto Alpha | June 3, 2019 | 1 | — |
| Tasuke | February 2002 | 1 | 1 |
| TATSUJIN | May 2017 | 2 | 1 |
| Tatsumi | August 25, 1970 | 1 | 1 |
| TDK | December 7, 1935 | — | 1 |
| Team GrisGris | 1998 | 2 | — |
| Team Ladybug | — | 1 | — |
| Team Ninja | 1995 | 51 | — |
| Team Silent | 1997 | 3 | — |
| Tech Arts Inc. | October 1996 | 1 | 2 |
| Technical Group Laboratory | July 1984 | — | 3 |
| Techno-Top | May 1999 | 1 | 1 |
| TechnoBrain | January 13, 1994 | 1 | 1 |