Leucojum aestivum L. is a bulbous Amaryllidaceae family plant. A pot experiment was conducted to investigate the impact of three different magnetic field (MF) intensities [50, 100 and 150 militesla (mT)] with three different exposure durations (1, 3 and 7 days) on growth parameters, alkaloid levels (galanthamine and lycorine), non-enzymatic antioxidant activities (total phenol-flavonoid content and free radical scavenging activity), and enzymatic antioxidant activities [superoxide dismutase (SOD) and catalase (CAT)] compared with control (no MF) in the bulbs and leaves. Maximum bulb length was achieved with 150 mT MF application for 3 days. Galanthamine levels increased by 63 % in the bulbs with 150 mT-7 days exposure and by 79.8 % in the leaves with 50 MT-1 day exposure compared to the control. The leaves and bulbs with 100 mT exposure showed the greatest increases in lycorine concentrations (23.8 % and 62.3 % rises, respectively). MF exposures of 150 mT for 3 days gave the best radical scavenging activity and total phenol-flavonoid content. The highest alkaloid levels in the bulbs were associated with higher SOD and CAT activity generated by MF treatments. This study revealed that the medicinal value and quantity of L. aestivum bulbs could be significantly increased with 150 mT MF intensity.