Climate change consequences are greatly affecting the development of agricultural crops. Olive trees are no exception, being faced with new challenges and threats associated with rising temperatures, frequent long drought periods and increasingly frequent extreme weather events. Flowering is one of the most important phenophases of the olive tree, and it can determine the climatic conditions of a climate in a year. Research on flowering phenology and analysis of number of flowers in bloom, morphological sterility and pollen germination was conducted on six domesticated varieties in the plantations of the Institute for Adriatic Crops and Karst Reclamation in Split and at the "National Collection of Domestic Olive Varieties of Croatia" in Vodnjan. Monitoring of flowering near Drobnica, Istarska bjelica, Kosmača, Levantinka, Oblica and Zuzorka was performed according to the RESGEN methodology for secondary characterization of olive varieties, ie determined using the BBCH scale during May and June 2021. The number of flowers in bloom and morphological sterility were determined by representative sampling of inflorescences on all sides of the canopy and by counting the total number of flowers and the number of sterile flowers. Pollen was collected in full bloom, left to germinate in medium for 24 hours, and then the percentage of germinated pollen grains for each variety was determined. It was concluded that varieties in the northern location (Vodnjan) begin flowering much later than in the south (Kaštel Stari / Split), the duration of flowering ranges from 6 to 10 days, and full flowering in all varieties lasts two days, with numerous overlaps, which allows cross pollination. Analysis of the inflorescences revealed that Drobnica, Istarska bjelica, Kosmača and Zuzorka had short inflorescences, while Levantinka and Oblica cultivars had the majority of medium inflorescences. Levantinka and Oblica have the highest percentage of staminate flowers at the Vodnjan location, and Oblica, Levantinka and Zuzorka at the Kaštel Stari / Split location, while Kosmača had the lowest percentage at both locations. Also, no major differences in the success of pollen germination were found among the examined varieties, and pollen germination ranges from 24.4% in Oblica to 41.6% in Zuzorka.