The liquid-liquid phase separation (LLPS) is often coupled with other ordering processes such as crystallization. In a polyolefin blend system, overwhelming changes in crystallization kinetics due to concentration fluctuation caused by spontaneous spinodal LLPS have been observed. Consequently, we are proposing a new mechanism of "fluctuation-assisted crystallization". In this process, the usual nucleation barrier could be overcome (or at least partially) by the spontaneous fluctuation growth of LLPS in the spinodal region. Time-resolved polarized optical micrographs for poly-(ethylene-co-hexene) (PEH)/poly(ethylene-co-butene) (PEB) = 40.60 isothermally crystallized at 117 degrees C for 2 min after LLPS at 135 degrees C as a function of LLPS time at 135 degrees C.