Essential oil composition, antimicrobial activity and flavonoid contents of leaf-fruits of Cedrus libani and Pinus nigra subsp. pallasiana were determined with GC-MS, disc diffusion method and HPLC in three different period. When the essential oil composition of leaf and fruits of P. nigra ssp pallasiana collected in April, July and September, major components were α-pinene, β-pinene, limonene, β-caryophyllene ve germacrene-D. On the other hand, additionally to these contents, myrcene and α–terpineol were also detected in C. libani. According to HPLC analysis, rutin, quercetin, kaempferol, naringin and resveratrol flavonoids were detected in different proportions. While rutin (154.33 µg g-) and resveratrol (20.02 µg g-) has the highest ratio in C. libani, quercetin (9.65 µg g-) and naringin (9.31 µg g-) were detected in P. nigra subsp. pallasiana along with rutin (39.66 µg g-). According to the antimicrobial activity results the essential oils of C. libani obtained in April has produced higher activity than that of July and September. On the contrary, the essential oils from P. nigra subsp. pallasina have produced the best antimicrobial activity on September compared to April and July. As a result, C. libani and P. nigra subsp. pallasiana essential oils have a composition showing antimicrobial activity and their harvesting season should be determined for the best and effective content.