- Main article: Soldier (XCOM: Enemy Unknown)
- Assault Class - specialized in run-and-gun tactics designed to rapidly take control of the battlefield and hold it.
- Heavy Class - specialized in delivering large-scale damage to an enemy through the use of explosive ordnance.
- Support Class - specialized in maintaining their allies and helping to hold ground on the battlefield.
- Sniper Class - specialized in long-range support with high damage dealing with one enemy at a time.
- Additionally every soldier has the possibility of gaining the following sub-class:
- Psionic Class: Every soldier has a random chance of possessing a set of psionic abilities, based on their Will. If unlocked, a soldier gains the abilities from this sub-class in addition to those from their original class.
This expansion introduces a new additional class:
- MEC Trooper - specialized operators of Mechanized Exoskeleton Cybersuits, these soldiers act as heavy fire support and cover destroyers with additional buff and melee options. Requires conversion of soldiers from their base classes via the Cybernetics Lab. MEC Troopers are not eligible to gain the Psionic Class.