When a Pokemon Mega Evolves, does it gain its stats that same turn?

Just want to know cuz weird things happen…Like my lucario speed maxed when mega evolved is 355 but for some reason my friends charizard hits first and his speed is 317

Pleaselog inorregisterto add a comment.

In all generations where Mega Evolution exists, all stats except Speed are recalculated and applied the turn a Pokemon Mega Evolves. Between Generations VI and VII, however, the Speed stat functions differently.

Generation VISpeed modifiers are applied the turnafterMega Evolving. This means a Pokemon retains its base form’s Speed on the turn it Mega Evolves. Additionally, Sableye’s Prankster will still take effect for the first turn of Mega Evolution despite the Mega form no longer having the Ability.

Generation VIISpeed modifiers are applied on the turn the Pokemon Mega Evolves. Sableye’s Prankster no longer gives priority to Mega Sableye’s moves on the first turn of Mega Evolution.

Mega Evolution (Bulbapedia)

The stats do increase, but whoever is faster before Mega Evolution will go first. If a Pokemon Mega Evolves from 85 Spd to 100 Spd, but my opponent’s Pokemon is at 86 Spd, it will go first, unless a priority move is used.