Booming Blade:
You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5 feet of you.
Extra attack:
Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.
I think we can agree that Booming Blade is casting a spell (a cantrip). Obviously I can’t use Booming Blade twice.
But does the fact that it’s a spell that makes a melee weapon attack count as “taking the attack action”?
In other words - if I cast Booming Blade, am I locked out of Extra Attack because I took a “Cast a Spell” action instead of an “Attack” action? Or do I still get an extra attack because casting the spell made me take the Attack action?
The action you’re taking is
Casting a Spell
.Attack
is a different action which would let you attack twice withExtra Attack
.You cannot Booming Blade your attacks with Extra Attack.
This is actually the topic of a Sage Advice:
Also, you actually can use Booming Blade twice in one turn because its a cantrip. The limit for spells cast only applies to leveled spells. The easiest way to Booming Blade twice is the Sorcerer metamagic Quicken Spell.
This is not worded completely correct; you can cast two leveled spells in one turn (using Action Surge). You just cannot cast a leveled spell in the same turn as casting a spell using a bonus action.
Yeah, Action Surge can do two leveled spells.