Question

Does defense stat affect the catch rate?

Answer 1

Nope. I caught Zekrom with a Great Ball, full health, 3 tries. It has 120 Def. I caught Skarmory in 5 tries with a Pokéball, it has 140 Def.

The higher it is will not affect the catch rate. However, I used an Electabuzz with Screech to reduce the defense, then I reduced the HP, and paralyzed Reshiram. Took one Pokéball to catch.

If you lower it, you may catch Pokémons easier. On the other hand, raising it has strictly nothing to do with it.

Comments

Just remember that Zekrom & Reshiram are easier than most legendaries to catch. :O

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True. But Zekrom's already got a good defense stat. 120 is not low.

Answer 2

According to Bulbapeida:

Approximately, the probability of catching a Pokémon starts with the
species' catch rate divided by 255. Then it is multiplied by the
following factors:
- The health of the Pokémon (relative to its full
health), which can reduce the probability to ⅓× at full health
- The type of Poké Ball, which can augment by some ×
- Any status ailment of the wild Pokémon (i.e. 2× increase for sleep or freeze, and 1.5× for
others).

So no, the defense of the Pokemon does not apply to it's catch rate.

Hope this helped!
~Excadrill444~