The effect of adding homopolymer poly(ethylene oxide) (PEO) on the sol/gel behavior of amphiphilic triblock copolymer Pluronic F127 ((EO)(98)(PO)(67)(EO)(98)) in aqueous media is explored. Emphasis is placed on the influence of the PEO molecular weight and concentration on micellization and gelation and the exploration of their correlation. PEO is always found to lower the critical micellization temperature modestly. However, short PEO chains promote the gelation of F127, and long chains delay or even curb gel formation. Micelle size measurements and cryo-TEM micrographs provide evidence for micellar aggregation via the bridging of long PEO chains or depletion flocculation, thereby impeding the ordering of micelles for gel formation.