The effect of antifoaming reagent, octyl alcohol, (OA), on the crystallization of poly(vinyl alcohol), (PVA), from its aqueous solution under steady‐state flow was investigated. The yield of precipitates was considerably influenced by the addition of small amounts of OA; it decreased with an increase of the contents of OA, and crystals were hardly produced from the solution which contained over 0,03% OA. The decreasing yield of precipitate by the addition of OA was clearly recognized for PVA with higher rel. mol. mass. The buildup of foams from the solution which contained OA was considerably restrained in comparison with that for the solution which did not contain OA.