Very few publications have documented the effects of climatic conditions on population fluctuation of Bactrocera oleae in the northeast part of the Mediterranean Basin. A field study (2005-2009) was carried out to analyze the population dynamics of B. oleae in the northern Balkans and to determine the potential correlation of population fluctuations of S. oleae and fruit infestation with abiotic parameters. The results of this study showed that despite the fact that climatic conditions had little direct influence on the population dynamics of adult males of B. oleae, minimum temperatures and precipitation have a significant effect on fruit infestation by B. oleae in the northern Balkans. The results further indicate that the annual population dynamic of the B. oleae in the northern Balkans is triple-peaked and is different from those observed in the southern Balkans. Better knowledge of seasonal population fluctuations of B. oleae in the northern Balkans could optimize the timing of insecticide applications in integrated control and thus reduce control costs and the risk of non-target effects and environmental contamination.