Games like Space Mercenary Defense Force
Games like Space Mercenary Defense Force include Vampire Survivors, Hades, Megabonk, Skul: The Hero Slayer, and Rogue Legacy. We matched them by the tags players give Space Mercenary Defense Force on Steam (Action, RPG, Indie, Action Roguelike, and Casual): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Action Roguelike · Indie · Action

Hades
Shared: Action Roguelike · Indie · Action

Megabonk
Shared: Action Roguelike · Indie · Roguelike

Skul: The Hero Slayer
Shared: Action · Indie · Action Roguelike

Rogue Legacy
Shared: Indie · Action · Action Roguelike

Death Must Die
Shared: Action Roguelike · RPG · Action

Halls of Torment
Shared: Action Roguelike · Action · RPG

Hades II
Shared: Action · Roguelike · Action Roguelike

Risk of Rain (2013)
Shared: Action Roguelike · Indie · Action

Dungreed
Shared: Action Roguelike · Action · Indie

The Binding of Isaac: Rebirth
Shared: Action Roguelike · Indie · Roguelike

Streets of Rogue
Shared: Action Roguelike · RPG · Action

Brotato
Shared: Action Roguelike · Roguelike · RPG

Boneraiser Minions
Shared: Action Roguelike · Indie · Action

Noita
Shared: Roguelike · Indie · Action

BALL x PIT
Shared: Action · Action Roguelike · Roguelike

Nuclear Throne
Shared: Action Roguelike · Indie · Action

The Binding of Isaac
Shared: Action Roguelike · Indie · Roguelike

UnderMine
Shared: Action Roguelike · RPG · Action

Magicite
Shared: RPG · Indie · Roguelike

Soulstone Survivors
Shared: Action Roguelike · RPG · Action

Hero Siege
Shared: RPG · Action Roguelike · Action

Juicy Realm
Shared: Action · Indie · RPG

Rogue Legacy 2
Shared: Action · Indie · RPG