Postharvest conditions have a noticeable effect on the quantity and quality of secondary metabolites of medicinal plants. Accordingly, in the present study, the effects of different storage durations (0, 2, 4, and 6 months) and packaging types (kraft, polyethylene, polypropylene, and without packaging) on the quantity and quality of essential oil and phenol and antioxidant activity of methanol extract in fennel (Foeniculum vulgare Mill.) fruit were evaluated. Essential oils and methanol extracts were prepared using hydrodistillation (Clevenger, for 3 hours) and Soxhlet extraction methods, respectively. Essential oils were analyzed by GC-FID and GC-MS. In general, increasing the storage duration reduced the essential oil content of fennel (with the exception of kraft packaging) and the rate of this reduction varied depending on the packaging type. The polyethylene-packed fruitsstored for 2 months and unpacked fruits stored for 6 months had the highest (3.25% v/w) and lowest (1.8% v/w) essential oil content, respectively. The number, type, and amount of essential oil compounds were affected by storage duration and packaging type. The highest (75.8%) and lowest (49.46%) amounts of E-anethole were obtained from the essential oil of unpacked fruits stored for 6 months and unstored fruits, respectively. The amount of phenol and antioxidant activity decreased with increasing storage duration, but the effect of packaging type varied at different storage durations. Overall, based on the essential oil content, phenol, and antioxidant activity, storage of fennel could not be recommended, but based on the type of target compound in the essential oil, different storage durations could be suggested. If the storage of fennel is necessary, the polyethylene and kraft packaging could be recommended based on the total characteristics measured in this research.