We found a new dendritic solidification morphology with secondary arms growing in eight directions rather than the < 1 0 0 > directions expected for a face-centered cubic (FCC) alloy. A bulk single crystal of a Ni-base gamma' single-phase alloy was cast by withdrawing method in a directional solidification furnace. The solidification structure was observed using scanning electron microscopy and analyzed using electron back-scatter diffraction. These results demonstrated that the growth direction of the primary dendrites was [0 0 1], which is known to be the preferred growth direction for FCC metals and alloys. However, the primary dendrite had eight secondary arms growing in the high-Miller-index directions between < 1 0 0 > and < 1 1 0 >. The main factor behind this new dendrite morphology is likely to be the anisotropic atomic stacking of L1(2) ordered phase, which is the primary phase of the investigated alloy.