Background: Currently, many studies focus on how the environment can be changed to encourage healthier eating behavior, referred to as choice architecture or "nudging." However, to date, these strategies are not often investigated in real-life settings, such as worksite cafeterias, or are only done so on a short-term basis. Objective: The objective of this study is to examine the effects of a healthy worksite cafeteria ["worksite cafeteria 2.0" (WC 2.0)] intervention on Dutch employees' purchase behavior over a 12-wk period. Design: We conducted a randomized controlled trial in 30 worksite cafeterias. Worksite cafeterias were randomized to either the intervention or control group. The intervention aimed to encourage employees to make healthier food choices during their daily worksite cafeteria visits. The intervention consisted of 14 simultaneously executed strategies based on nudging and social marketing theories, involving product, price, placement, and promotion. Results: Adjusted multilevel models showed significant positive effects of the intervention on purchases for 3 of the 7 studied product groups: healthier sandwiches, healthier cheese as a sandwich filling, and the inclusion of fruit. The increased sales of these healthier meal options were constant throughout the 12-wk intervention period. Conclusions: This study shows that the way worksite cafeterias offer products affects purchase behavior. Situated nudging and social marketing-based strategies are effective in promoting healthier choices and aim to remain effective over time. Some product groups only indicated an upward trend in purchases. Such an intervention could ultimately help prevent and reduce obesity in the Dutch working population. This trial was registered at the Dutch Trial Register (http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5372) as NTR5372.