The agricultural industry is intensifying production methods to increase crop yields. Olive cultivation, the prevalent permanent crop in Europe and the Mediterranean area, involves intense practices with heavy agrochemical use. This significantly impacts agroecosystem biodiversity and its ecosystem services. In this study, we explore how biodiversity influences the adult olive fly (Bactrocera oleae (Rossi)) population in Lesvos Island, Greece, under different understorey management practices in olive groves. Our findings show that increased plant and arthropod abundance and diversity negatively affect the olive fly. The results suggest that maintaining undisturbed plant cover enhances olive grove biodiversity, ecosystem services, and biological control of the olive fly. Moreover, this practice is in line with Integrated Pest Management principles and Conservation Biological Control approach.