Games like Catnip Wars
Games like Catnip Wars include Bloons TD 6, Plants vs. Zombies GOTY Edition, Rogue Tower, Age of Darkness: Final Stand, and Legion TD 2 - Multiplayer Tower Defense. We matched them by the tags players give Catnip Wars on Steam (Strategy, PvE, Casual, Tower Defense, and 3D): closest matches first, and among equally close ones the better-known games.

Bloons TD 6
Shared: Strategy · Tower Defense · Casual

Plants vs. Zombies GOTY Edition
Shared: Strategy · Tower Defense · Casual

Rogue Tower
Shared: Strategy · Tower Defense · Casual

Age of Darkness: Final Stand
Shared: Strategy · Tower Defense · PvE

Legion TD 2 - Multiplayer Tower Defense
Shared: Strategy · Tower Defense · PvE

Orcs Must Die! 3
Shared: Strategy · Tower Defense · PvE

They Are Billions
Shared: Strategy · Base Building · Tower Defense

Thronefall
Shared: Strategy · Tower Defense · Base Building

Bee Island
Shared: Strategy · Tower Defense · Base Building

Mindustry
Shared: Tower Defense · Strategy · Base Building

Emberward
Shared: Strategy · Tower Defense · 3D

Outpost: Infinity Siege
Shared: Tower Defense · 3D · Base Building

Warhammer 40,000: Dawn of War - Definitive Edition
Shared: Strategy · PvE · Base Building

Kingdom Rush - Tower Defense
Shared: Strategy · Tower Defense · Casual

Plague Inc: Evolved
Shared: Strategy · Casual · Zombies

Tower Dominion
Shared: Strategy · Tower Defense · Base Building

Predecessor
Shared: PvE · Third Person · Strategy

Kingdom Rush Origins - Tower Defense
Shared: Strategy · Tower Defense · Casual

Age of Mythology: Retold
Shared: Strategy · 3D · Base Building

DG2: Defense Grid 2
Shared: Strategy · Tower Defense · Base Building

Dyson Sphere Program
Shared: Base Building · Strategy · Sci-fi

Vectorio Classic
Shared: Strategy · Tower Defense · PvE

Taur
Shared: Strategy · Tower Defense · Base Building

XCOM: Enemy Unknown
Shared: Strategy · Tactical · Sci-fi