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The early-stage M₂₃C₆ morphology at the phase boundary between austenite and δ ferrite grain in Type 304L austenitic stainless steel was investigated with transmission electron microscopy (TEM). The M₂₃C₆ has coherency with austenite grains at phase boundary. The phase boundary between the M₂₃C₆ and austenite grains has curved appearance. The curved phase boundary might be a faceted interface composed of (111) plane and the other low-index planes on the atomic scale. The M₂₃C₆ morphology at the phase boundary was identified to be a complex pyramid-like shape that has {111}, {110} and {100} interfaces. The slight deviation in the angle measured between edges of carbide in the TEM images from that calculated between edges expected from the M₂₃C₆ morphology might be attributed to multilayer growth in the interior region of the M₂₃C₆ face.