One aspect of this titanium carbonitride-based cermet insert has a microstructure including 75 to 90 area % of a hard phase and the balance as a binding phase, wherein the hard phase includes a first hard phase in which a core-having structure includes a TiCN phase and a peripheral portion includes a (Ti,W,Ta/Nb)CN phase, a second hard phase including a (Ti,W,Ta/Nb)CN phase, and a third hard phase including a TiCN phase, and the binding phase contains 18 to 33% of Co, 20 to 35% of Ni, 5% or less of Ti and Ta and/or Nb, and 40 to 60 mass % of W. In another aspect of this cermet insert, a total of an amount of Ti converted as carbonitride, an amount of Ta and/or Nb converted as carbide, and an amount of W converted as carbide is 70 to 95 mass %, an amount of W converted as carbide is 20 to 35 mass %, and Co and Ni are 5 to 30 mass %, this cermet insert has a microstructure including a hard phase containing (Ti,W,Ta/Nb)CN and a binding phase containing, as main components thereof, W and Co and/or Ni, and 40 to 65 mass % of the W is contained in the hard phase. This cutting tool includes a holder and the cermet insert described above held and fixed by the holder.