Pennycress has been suggested as an alternative feedstock for bioenergy. Especially, its cultivation in a double-cropping system with corn appears to be promising for a sustainable production. As an aspect of its sustainability, we studied the effect of a pennycress-corn double-cropping system on spider diversity. We used a randomized block design with 60 pitfall traps to compare the system's spider diversity with that of three commonly applied corn rotations: mustard-corn, green fallow-corn and bare fallow-corn. We sampled from 13 March to 26 June 2012, which included the corresponding cultivation changes to corn. The pennycress-corn system harboured a higher spider species richness and diversity (Shannon index) than the other three systems, driven by web-building spiders. Abundance only differed between the pennycress- and bare fallow-corn system. However, separated into foraging guilds, hunting spiders were most abundant in the mustard-corn system, whereas web-building spiders were more abundant in the pennycress-corn than in the mustard- and bare fallow-corn system. The results obtained in the present study suggest that cultivation of pennycress as a biofuel feedstock in a double-cropping system has positive (and not negative) effects on the spider diversity compared with other commonly used cultivation systems.