Games like Defend Your Castle
Games like Defend Your Castle include Plants vs. Zombies GOTY Edition, Kingdom Rush - Tower Defense, Orcs Must Die!, Town of Salem, and Witch It. We matched them by the tags players give Defend Your Castle on Steam (Strategy, Indie, Casual, Action, and Survival): closest matches first, and among equally close ones the better-known games.

Plants vs. Zombies GOTY Edition
Shared: Strategy · Casual · Comedy

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

Orcs Must Die!
Shared: Strategy · Action · Indie

Town of Salem
Shared: Strategy · Indie · Casual

Witch It
Shared: Casual · Indie · Action

Bloons TD 5
Shared: Strategy · Action · Casual

Bloons TD 6
Shared: Strategy · Casual · Tower Defense

Totally Accurate Battle Simulator
Shared: Strategy · Funny · Indie

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

CastleStorm
Shared: Indie · Strategy · Action

Kingdom Rush 5: Alliance TD
Shared: Strategy · Fantasy · Indie

Rock of Ages
Shared: Strategy · Indie · Comedy

Who's Your Daddy?!
Shared: Strategy · Funny · Comedy

Dungeon Defenders
Shared: Strategy · Survival · Indie

Game Dev Tycoon
Shared: Indie · Strategy · Casual

There's Poop In My Soup
Shared: Casual · Indie · Funny

Rock 'N' Roll Defense
Shared: Strategy · Casual · Action

Goat Simulator
Shared: Comedy · Funny · Casual

A Dance of Fire and Ice
Shared: Indie · Fantasy · Casual

Rhythm Doctor
Shared: Indie · Action · Strategy

Idle Champions of the Forgotten Realms
Shared: Strategy · Fantasy · Indie

Timberman
Shared: Casual · Indie · Action

Orcs Must Die! 2
Shared: Strategy · Action · Indie

The Escapists
Shared: Strategy · Indie · Action