Recent reports indicate that vegetative growth and yield of C3 crops are enhanced by foliar methanol application and that overall crop water use is reduced by methanol sprays. In order to evaluate the effects of methanol and barnyard grass density on rice (Oryza sativa cv. Shiroudi) yield and its components, a field experiment was conducted at the Rice Research Station of Tonekabon, Iran in 2012. The experiment was carried out as a randomized complete block design with a factorial arrangement in three replicates. Studied factors were aqueous methanol solutions (0, 6, 12, 18 and 24% (v/v)) and barnyard grass (Echinochloa crus-galli) densities (0, 16, 24 and 32 plants m-2). Methanol was sprayed on the foliage of rice three times during its growth period with two-week intervals. Results indicated that effect of methanol was significant for tiller number and grain yield (P < 0.05), while the effect of barnyard grass density was significant for grain and biological yields (P < 0.01). Moreover, the interaction between methanol and barnyard grass density was significant for grain yield (P < 0.05) and 1000-grain weight (P < 0.01). The greatest mean values for grain yield and 1000-grain weights obtained at 18% (v/v) with weed-free condition, with 7440.8 kg ha-1 and 28.07 g, respectively. Under weed-free conditions grain yield increased as methanol dose increased from 0 to 18% (v/v) and then reduced significantly. At the highest weed density, grain yield decreased significantly as the methanol dose increased. It appears that foliar sprays of aqueous methanol may be recommended for rice under weed-free conditions.