This research assessed the seasonal variation in the chemical composition and biological activities of essential oils extracted from Thymus linearis Benth. in rainy season and winter season. The essential oil highest yield was recorded in the rainy season. The oils were analyzed by GC and GC-MS. Thymol was the marker component in both oils with varying compositions, i.e., 31.9% in rainy season oil and 35.7% in winter season oil. While assessing the biological activities, the antioxidant activity of the oils was investigated in vitro using three assays: DPPH radical scavenging activity, H2O2 radical scavenging activity and metal chelating activity. The highest antioxidant capacity was observed in oil extracted in winter season. Winter season oil showed good inhibition of protein denaturation (IC50 = 26.55 ± 0.03 μg/mL) as compared to the rainy season oil. The oils inhibited the activity of α-amylase with IC50 of 32.27 ± 0.05 μg/mL (winter) and IC50 of 32.87 ± 0.04 μg/mL (rainy). Insect antifeedant activity performed using the leaf dip method against Spodoptera litura afforded significant results with slight variations. Essential oils were also tested against Meloidogyne incognita for nematicidal activity and inhibition of eggs hatching potential in laboratory conditions. Moreover, it was found that activity level of oils was seasonal dependent. The pharmacological activities of the major components were also predicted using the web-based software Pass.