四海兄弟中的武器和其所处的时代是相同的。下面罗列了《四海兄弟：失落的天堂》中的所有武器。
单手武器[]
- S&W Model 10 M&P
- Caliber: .38
- Capacity: 6 rounds
- Colt Detective Special
- Caliber: .38
- Capacity: 6 rounds
- S&W Model 27 Magnum
- Caliber: .357 Magnum
- Capacity: 6 rounds
- Colt 1911
- Caliber: .45 ACP
- Capacity: 8 rounds
双手武器[]
- Thompson 1928
- Caliber: 45 ACP
- Capacity: 50 rounds
- Sawed-off Shotgun
- Caliber: 12 Gauge
- Capacity: 2 shells
- Pump-action Shotgun
- Caliber: 12 Gauge
- Capacity: 8 shells
- Mosin-Nagant 1891/30
- Caliber: 7.62MM
- Capacity: 5 rounds
- US Rifle M1903 Springfield
- Caliber: .30-06
- Capacity: 5 rounds
投掷类武器[]
- Grenade
- Capacity: Single use
- Molotov Cocktail
- Capacity: Single use
近战类武器[]
- Baseball Bat
- Knife
- Crowbar
- Knuckle-duster
- Steel Bar
- Wooden Plank