Apple is renowned for its nutritional as well as economical value. The success of newly introduced apple varieties highly depends on a clear understanding of their floral biology and pollination behaviour, which are crucial for ensuring optimal fruit set, yield and quality. Therefore, the present investigation was carried out at Regional Horticultural Research and Training Station, Mashobra, Shimla, Himachal Pradesh, India during the year 2023 and 2024 to study the floral biology of different apple varieties and to study the extent of fruit set under different modes of pollination. Five main varieties viz. Red Velox, Red Cap Valtod, Jeromine, Scarlet Spur II and Modi along with three pollinizing varieties viz. Auvil Early Fuji, Dark Baron Gala and Redlum Gala were selected for different studies. Marked variations in the floral characters like flower size, petal arrangement, stamen number, pistil length and ovary diameter were recorded. Flowering duration was longest in Dark Baron Gala (15 days) during 2023 and 2024 and shortest (10 days) in Scarlet Spur II and Red Velox in both years. Maximum (88.78 %) mean pollen viability was observed in 1 per cent acetocarmine and minimum (87.70 %) in erythrosine B. In vitro pollen germination was maximum (61.83 %) in Dark Baron Gala and minimum (40.86 %) in Scarlet Spur II. Average fruit set was found to be highest (63.66 %) under open pollination conditions followed by controlled/hand-pollination conditions (51.13 % and 53.85 %) during 2023 and 2024 and lowest (22.33%) under bagging. Similarly, mean fruit retention was highest (73.14 %) under open pollination conditions followed by controlled/hand pollination conditions (54.90 % and 69.42 %) during 2023 and 2024 and lowest (59.05 %) under bagging. Maximum values of fruit length, breadth and weight were recorded under bagging condition followed by open pollination, whereas, minimum fruit length, breadth and weight under controlled/hand pollination conditions. On the basis of present investigation Dark Baron Gala showed all the characteristic of ideal pollinizing variety viz. synchronization in flowering, pollen viability, pollination behaviour and extent of fruit set with over all commercial accessibility.