When Vikings Attack! plays like an arena melee brawler game. The only hard rule is that throwing objects are only allowed. Players control a small group of civilians fighting hordes of vikings. The objective is to pick up objects and throw to knock out enemies. Every vikings and civilians are fragile to every strike from a thrown object and will be knocked out in one hit. Each time an object collides with a figure, they're knocked out and excluded from the group, but larger or wide objects may even knock out an entire group, resulting in the player being eliminated. Lost civilians can be replaced by recruiting stray people roaming field. The game also features special items to be thrown such as explosive bombs for an area of effect attack.