"Serious Sam: The Second Encounter" offers numerous multiplayer options including the highly acclaimed "Serious Warped Deathmatch" MOD (Version 3) created by A Few Screws Loose. Players can join forces against the swarm of enemies in cooperative play through all single-player levels, an option rarely delivered in the first-person shooter genre. Players may utilize the multiplayer option via LAN and Internet for up to 16 players in six different multiplayer modes and over 20 multiplayer maps. Title also includes exclusive split screen support on a single computer for up to four players.

Other serious features include: - Seven new fiends added to Mental's evil army, in addition to all your old enemies
- Over 20 multiplayer levels
- Three all new weapons: Flamethrower, Sniper Rifle with 8X zoom and the ultra-wicked Chainsaw
- 12 new single player levels plus over 15 multiplayer levels for Scorematch and Deathmatch - a HUGE addition to the "Serious Sam" Universe
- Four power-ups: Serious Speed, Serious Damage, Invulnerability and Invisibility for a twist to the classic Doom-style gameplay "Serious Sam" is famous for
- Seriously Warped Deathmatch right out of the box, plus expanded Deathmatch straight from Croteam