Does Moxie/Speed Boost effect stay after my Pokemon mega evolves?

Question

For example if I defeat opponents Pokemon with moxie Salamence and then mega evolve it will my Salamence be at +1 ATK or the moxie buff will fade?

Answer 1

Althought the Ability will change upon Mega evolving, the stat boosts of certain Abilities will remain, as they are indirect. Moxie and Speed Boost give 'normal' or 'indirect' boosts to stats, much like moves does. The stat is raised the same way as if you had used Howl or Agility. Changing abilities dont effect these stats, and as such they stay until you switch out the Pokemon.
This does not apply to all abilities however. Abilities that give a power boost directly such as Huge Power or Aerielate wont remain when changing Abilities.
Source: Experience and http://replay.pokemonshowdown.com/pokemondatabase-ubers-10575

Comments

Your opponent seems like a real expert. That Greninja set looks really good.

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Just sayin', Aerialate is only available to Mega Pokémon, not to regular Pokémon. Having it as an example is sort of unnecessary.

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It doesn't matter if it's unnecessary, the principle still stands either way. That makes your comment completely unnecessary -.-;

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I don't understand your logic; there is no need to use Aerialte as an example beacause it is not an ability lost through Mega Evolving, because the only Pokémon who have access to it gain it by Mega Evolving. I'll drop the issue, no use arguing.

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Than you very much for the explanation :)

Answer 2

Because Salamence gets a different ability when it Mega Evolves, yes, the Moxie effect will be lost when you Mega Evolve to get an Aerilate Salamence.

I believe this is the case with all Mega Evolutions as all of them get a different ability when they evolve, but if I'm wrong I hope one of you can correct me.

Hope I helped. :)
Source