Anaerobic digestion (AD) is an interesting and sustainable option to handle sewage sludge (SS), as it generates a methane-rich biogas and a digestate with potential fertilizing properties. Several strategies have been proposed to enhance AD performances and the valorization of SS. Among these, the application of a static magnetic field (SMF) has been poorly evaluated and recently gained attention. This work investigated the effect of low-intensity SMF (20-50 mT) on methane production from AD of SS, comparing it to the effect deriving from the application of a high-intensity SMF (1.5 T). Magnetic pretreatment at 20 mT was particularly effective, as it increased biomethane production up to 12.9% compared to the control test. On the contrary, 1.5 T was detrimental in terms of cumulative methane production, as it resulted in a 20.9% decrease. These outcomes suggest that SMF intensity is inversely related to biomethane generation and that further investigations are worthy to understand the mechanisms underlying AD enhancement by SMF application.