|Founded||2030-2031 (exact date unknown)|
|Headquarters||Amadeus base, location unknown (somewhere in Oceania)|
|Area of Operations||Worldwide|
|Enemies With|| Regular Army|
Ptolemaic Army (Metal Slug Attack)
Rebel Army (mainly neutral)
Martians (Metal Slug Attack)
Invaders (Metal Slug Attack)
|Affiliated With||Rebellion Army (Metal Slug 4)|
The corporation was destroyed during at the end of the White Baby Crisis, where the Regular Army infiltrated their headquarters and defeated Amadeus, causing the base to self-destruct.
The Amadeus Syndicate appears as a small organization due to the game reusing weapons and infantry from other armies. The Syndicate is in the Independent Faction in Metal Slug Defense and Metal Slug Attack because of this.
In Metal Slug Attack, the Syndicate's forces has been expanded and now sport a violet and gray motif. Infantry's uniforms are colored purple to contrast the Regular Soldiers' blue uniforms. The Syndicate are still in good terms with the Rebel Army.
AR-10 MG Infantry/Amadeus Corporal: Armed with 7,62mm AR-10 Autorifle, they are the elite legion of the Amadeus Syndicate. Some of them have the honor to serve as personal guards of Amadeus. They are very dangerous in comparison to other infantry. In Metal Slug Attack, they are capable of crouching for better firing and accuracy
Amadeus Soldier (Bazooka): Soldiers on board of the Brave Guerrier are similar to the Rebel Bazooka but spawn in groups. Those on foot fire larger shots that have unlimited range. Paratroopers have rapid fire and are able to stun their enemies but lose both abilities when on ground.
Amadeus Rocket Bomb Soldier: Throws up to five rockets that are able to block enemy projectiles.
Hazmat Soldiers: Amadeus Infantry invading the Haunted House attractions. Yellow Hazmat Soldiers patrol the zombie attraction and throw grenades. Green Hazmat Soldiers patrol the Egyptian attraction and toss bowling ball grenades that spawn mummies. Hazmat soldiers have higher body protection.
- Amadeus (The Doctor)
Most of the ground vehicles are from the Rebel Army. In Metal Slug Attack, these are recolored gray to differentiate from the Rebel versions. Remakes of larger weapons are colored purple.
- Brave Guerrier
- Toschka Dalanue (+ MK II)
- The Iron
- Iron II
- Prototype Iron (+ MK II)
- Iron Fortress
- Big John
- Jade John
- Real John
- Sea Satan (Aquatic)
- Sea Satan + (Aerial)
- Sea Satan II (Based on the S.S.+)
- Amadeus Mother Computer
- Hairbuster Riberts (Amadeus)
- Hi-Do (Amadeus)
- Di-Cokka (Amadeus)
- M-15A Bradley (Amadeus)
- Nop-03 Sarubia (Amadeus)