Climate change, recent droughts, and increasing salinity of water and soil in pistachio-growing regions of Iran, along with the sensitivity of some existing cultivars, have reduced orchard productivity. To improve yield per unit area, practices such as top-working, rejuvenation of old trees, and cultivar replacement are critical issues that must be considered. Therefore, this project was conducted from 2021 to 2025 at the Pistachio Research Station of the Agricultural and Natural Resources Research and Education Center of Qazvin. In March 2021, 20-year-old Owhadi trees grafted on Qazvini rootstocks, which had shown poor productivity, were headed back, and bud grafting was carried out in spring 2021. Treatments included Owhadi (without heading back and grafting), Ahmadaghaei, Akbari, and Kalehbozi cultivars. Vegetative growth parameters of grafted shoots (current shoot length and diameter) as well as quantitative and qualitative fruit traits of the cultivars were evaluated. Results showed that top-working improved yield and fruit quality of pistachio. Yield increased from 566.6 g in Owhadi (without top-working) to 1616 g in Kalehbozi, 1350 g in Ahmad-Aghaei, and 966.9 g in Akbari. The greatest and smallest current shoot length and diameter belonged to Akbari and Owhadi, respectively. The highest and lowest number of clusters per shoot and nuts per cluster were observed in Kalehbozi and Owhadi, respectively. Kalehbozi and Ahmadaghaei cultivars exhibited the highest dry weight and percentage of split nuts. The lowest (23) and highest (33) nut ounce values were recorded in Akbari and Kalehbozi, respectively. The lowest percentage of split nuts (51.33%) and the highest percentage of blanks (17.3%) were observed in Owhadi. Based on the results, the Owhadi cultivar, due to having the highest blankness, the greatest closed‑mouth nuts, and the lowest yield, was not suitable for the Qazvin region. In contrast, the Kallehbozi and Ahmadaghaei cultivars showed better adaptability to the area.