The research was carried out during 2015 and 2016 seasons at Arab El-Mulk village, Banias district, in Tartous Governorate, to study the effect of planting peanut seeds size (mixture, small, medium and large), and spraying plants with bread yeast (Saccaromyces serevisiae) concentration of (4%) in three treatments (control, once and twice), on biological yield (BY), Economic yield (EY) and some physiological indicators; yield index (YI), Harvest index (HI), crop index (CI) and seed index (SI). The experiment design was set as split plot in a randomized complete block with four replications. The seeds size considered the main factor, while spraying yeast allocated the sub plots. The results showed that seed size caused significant increases in all of the studied indicators. The large seeds gave better values of (BY) 210 g, (HI) 30.56%, (CI) 44.12%, (SI) 74.85 g, except (EY) compared with mix, small and med seeds. Also the results showed that there were no significant increase between mixture and medium seed size in (YE) and (HI), but there was a significant increase in (BY) and (SI), on the other hand the treatments; spray yeast for once and twice had significant increases compared to the control, and the twice yeast spraying gave better values (215.22 g ,63.98 g, 29.64%, 42.37 % and 73.45g ) of (BY , EY ,HI, CI and SI) respectively, compared to the control. The interaction between seeds size and bread yeast spraying caused a significant increase which achieved 15.78 % in (BY), 23.99 % in (EY), 9.74 in (HI), 13.68% in (CY) and 7.87g in (SI) compared to the interaction between untreated treatment and small seeds size.