Pistachio are one of the most important horticultural products that play an important role in the country's economy. Although the existence of some nutritional and management problems has reduced the productivity of this product. The present study was conducted in order to evaluate the application of carrageenan algae extract on some traits including leaf area, chlorophyll index, percentage of blankness, percentage of deformed fruits and yield. The experiment was conducted in the year 2021 in a commercial garden in Zarand city in a factorial format in the form of a randomized complete block design with four replications at two times, 10 and 20 days after flowering. Treatments included carrageenan algae extract with concentrations of 0, 0.5, 1 and 1.5 mg/l. The results showed that carrageenan 1 mg/l had the greatest effect on the leaf surface, chlorophyll index, percentage of blankness, percentage of deformed fruits and yield in both foliar application times compared to the control. In general, 1 mg/l carrageenan had the greatest effect on the improvement of vegetative and reproductive traits in pistachio trees of Ohadi cultivar.