Three different treatments of seaweed extract (Ascophyllum nodosum) were applied at five different stages of growth, as foliar applications, to examine their effects on yield and quality criteria in peppers (cv. California Wonder) Each treatment caused an increase in fruit yield, and a 10-day earlier first harvest was observed in treatment groups (trt-1, trt-2 and trt-3) compared with control. Fruit length and fruit diameter significantly increased with increased seaweed extract treatment. Nevertheless, the difference between treatments was not significant in wall thickness of fruits. Soluble solids and chlorophyll contents increased whereas titratable acidity decreased in line with the seaweed extract treatments. However, there was no significant difference between control and the seaweed extract treated groups in terms of pH of the fruits. Lt was concluded that trt-2 (340g/da) gave the best results with regard to fruit yield and quality.