Menu-based ‘nudges’ hold promise as effective ways to encourage a shift away from ruminant meat and towards more environmentally friendly plant-based food when dining out. One example of a menu-based nudge is including an inferior ‘decoy’ option to existing items on menus. Decoys have been shown to influence decision-making in other domains (e.g. Lichters, Bengart, Sarstedt, & Vogt, 2017), but have yet to be used to promote sustainable food choices. Two online randomized controlled trials tested whether the addition of higher priced ‘decoy’ vegetarian options on menus influenced the number of diners choosing a ‘target’ vegetarian option. Adjusted Generalized Estimating Equations on data from four menu conditions showed no main effect of the intervention in study 1 (decoy absent vs. decoy present; Odds Ratio (OR) 1.08 95% Confidence Interval (CI) 0.45 to 2.57). Replicating the trial in study 2 across seven menu conditions and testing a more expensive decoy also showed no main effect of the intervention decoy absent vs. decoy present; OR 0.68 (95% CI 0.41 to 1.12). Further analyses revealed that our price-based decoy strategy (a 30% price increase) did not significantly influence the number of people choosing the inferior decoy dish, possibly because dish choices were purely hypothetical. Further research is needed to clarify which attributes of a dish (e.g. taste, portion size, signature ingredients etc.) are optimal candidates for use as decoys and testing these in real world choice contexts.