The combat in Mass Effect resembles a third-person shooter, but is actually powered by an RPG rules set. You can draw your weapon by pressing the X button (Q on the PC) or either of the triggers (mouse buttons on the PC), and can holster it by pressing the B button (Q on the PC).

Drawing your weapon enters combat mode, showing a reticule on-screen to indicate where your weapon is aimed. It also displays the status of each squad member in the lower left corner of the screen. The red bar indicates the health of each squad member, while the blue boxes indicate the status of each character's shields. More boxes mean greater shield strength, and empty boxes mean the shields are depleted.

Radar is displayed in the bottom right corner, and shows enemies as red dots. Some enemies can jam your radar, hiding their locations from you. However, certain weapon upgrades can be used to negate this ability.

The right analog stick (or mouse on the PC) is used to aim the target reticule. Holding the left trigger (right mouse button on PC) zooms in for more precise aiming, increasing your character's accuracy. The reticule turns orange when it is placed over an enemy or any object that can be damaged or destroyed. Squeezing the right trigger (left mouse button on PC) then fires your weapon. The chance of hitting an enemy and how much damage is dealt from your weapon are determined by your stats and equipment. Your chance of hitting an enemy is reduced by holding the trigger for a long period of time. Sustained fire can also overheat your weapon, meaning you must wait for it to cool down before using it again.

On the Xbox 360, strategic management is accomplished through the use of two combat "wheels." The first is the "Weapons Wheel" which is accessed by holding down the left bumper. This pauses the action, and allows you to select what weapon each member of your squad will use. All squad members carry a pistol, shotgun, assault rifle, and sniper rifle, but each will be far more effective with a certain weapon if they have trained in its use.

The second wheel is the "Power Wheel," which is accessed by holding the right bumper. This allows you to access the special abilities of all squad members and use them accordingly by aiming using the right analog stick. A power can also be mapped to the right bumper by pressing the X button while using the wheel.

On the PC these wheels are replaced by the Tactical HUD, which is accessed by
holding down the Spacebar. This screen shows the abilities that are available to you and your squad members. You can use it to select which weapons and powers to use, and it also allows you to set your hotkeys for each ability by dragging them to the quick slots located in the upper left corner. Here they can be accessed by pressing the appropriate number key, 1 through 8.