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The study has been carried out to determine effects of Harpin treatment on fruit set and fruit quality characteristics on 0900 Ziraat Sweet cherry cultivar, which has low fruit set problem. The study was carried out in Suşehri, a district of Sivas in 2015, Turkey. As plant material in the study, it was used five old trees of 0900 Ziraat’ sweet cherry variety grafted on MaxMa 14 rootstock. 125, and 250 mg L-1 doses of Harpin was applied both once and twice. While the first application was made at 10 % full bloom (17 April), the second application was made one month before commercial harvest (22 May). Compared to the control, it was determined that Harpin had a significant effect on fruit set on 0900 Ziraat Sweet cherry cultivar. While the fruit set ratio in control treatment was 11.8 %, this ratio reached to 22.0 % with twice 250 mgL-1 Harpin treatment. One of the most significant results of the study is that both increasing number of treatments and increasing amount of dosage led to an increase in fruit set as well. The fruit quality characteristics such as fruit size, fruit color, pH, SCC and titratable acidity was not affected by Harpin treatment. However, differences on fruit firmness and stem retention force between treatments were statistically significant