The citrus trade market welcomes cultivars with different characteristics such as being totally seedless or having fewer seeds, having thin and vividness skin, high ratio of sugar to acid, being watery, easy peeling and relatively large fruit. Furthermore, a wide range of cultivars should be available according to fruit ripening time from very early (precocious) to very late (serotinous). ‘Yashar’ mandarin is a hybrid obtained by crossing of the ‘Minneola’ tangelo and ‘Changsha’ mandarin. The fruits of this cultivar grow in the northern regions of Iran, and it ripen in May, thus, they are considered the late-ripening mandarin cultivars. One of the deficiencies of this cultivar is that it is full of seeds (25-30). Two separate experiments were performed to reduce the number of seeds in ‘Yashar’ mandarin. In the first experiment; the effect of pollen grains of different citrus cultivars (‘Valencia’ orange, ‘Hamlin’ and sour orange) and a free-pollination treatment as a control group was evaluated. In the second experiment, the effect of foliar application of copper sulfate at the rate of 25 mg·L-1 was conducted in stages 30, 60 and 80 % of open flowers. One free pollination treatment as a control group was evaluated as well. The results showed that the highest index of fruit technology (multiplication of the percentage of the extract in the soluble solids divided by 100) was obtained by pollination with ‘Hamlin’ and sour orange pollen grains. The foliar spraying with copper sulfate, when 30 % of the flowers had opened, among all the treatments evaluated in the study, reduced the number of seeds in the Yashar mandarin cultivar.