The online grocery retail industry is rapidly growing and has to improve order picking activities which is one of the most costly and labor-intensive activities of their supply chain. Gamification has been promised to increase the motivation and productivity of order pickers, but empirical findings in real world work environments are still missing. In this case study, a gamified design was tested during an intervention with professional order pickers. The design contained the following game elements: points, badges, leaderboards, performance graphs and avatars. The results show that the motivation of the order pickers are positively influenced by the intervention and that this led to a higher productivity. Besides, it was found that different game elements were differently appreciated depending on the level of experience of the order picker.