The　delta　(δ)　processing　strategy　is　an　efficient　heat　treatment　to　refine　and　homogenize　the　grain　microstructure　of　Inconel　718　superalloy　(IN718).　However,　the　microstructure　becomes　complicated　by　the　effect　of　pre-precipitated　δ　phases,　due　to　the　coupling　of　precipitations,　high　temperature,　and　loading　stress.　The　present　study　aims　to　clarify　the　effect　of　δ　phases　on　the　microstructure　evolution　of　IN718,　especially　the　promoting　effect　on　deformation　twins　(DTs)　and　dynamic　recrystallization　(DRX)　behavior.　The　results　show　that　the　promoting　effect　of　δ　phases　on　the　formation　of　DTs　was　attributed　to　the　lower　stacking　fault　energy　(SFE)　caused　by　the　precipitation　of　δ　phases　and　the　local　stress　concentration　caused　by　the　distribution　of　δ　phases.　The　area　fraction　of　DRX　grains　in　the　compressed　δ-containing　specimen　was　21%　higher　than　that　in　the　compressed　δ-free　specimen,　which　was　associated　with　the　discontinuous　dynamic　recrystallization　(DDRX)　nucleation　stimulated　by　the　single　δ　phase　and　the　continuous　dynamic　recrystallization　(CDRX)　nucleation　promoted　by　the　distribution　of　δ　phases.　Furthermore,　a　novel　heteroepitaxial　recrystallization　(HERX)　mechanism　was　found　based　on　inverse　precipitation　from　the　undissolved　δ　phase　to　γ　matrix　phase　grains　with　a　crystallographic　orientation　relationship　of　(0_10)[1　0　2]δ//(__111)[0　1　1]HERX.　©　2023