The paladin's Improved Divine Smite 11th-level feature gives every melee weapon attack an extra 1d8 radiant damage.
Their 2nd-level Divine Smite feature does 1d8 additional damage to fiends and undead when they expend a spell slot to smite.
Does Improved Divine Smite deal additional damage to fiends and undead as Divine Smite does, without expending a spell slot to use Divine Smite?
Best Answer
No, Improved Divine Smite does not do extra damage to fiends and undead
Improved Divine Smite says:
There is no mention of extra damage for fiends and undead so no extra damage is done (beyond the 1d8 extra it does to every creature of course). Contrast this with Divine Smite which says:
Without that line of text there is no reason to think that Improved Divine Smite does the same thing. The two abilities are completely separate from each other despite the similarity in the names.
However, note the last line of Improved Divine Smite which states that Divine Smite and Improved Divine Smite can be used together and thus the extra damage against fiends and undead can be added to Improved Divine Smite albeit at the cost of a spell slot.