To realize the potential environmental benefits that recycling and/or composting bio-based plastic packages can deliver, it is important that consumers view bio-based packaging as environmentally-friendly, but also correctly dispose of the packaging. The current experimental lab-in-the-field study was conducted among German consumers (n = 281) and explores whether consumers' perceived environmental benefits of recyclable and compostable bio-based plastic packages match with how consumers dispose of these packages. The results show that consumers only perceive compostable bio-based packages to have more environmental benefits than fossil-based packages. However, consumers dispose of compostable bio-based packages in an incorrect manner (not in line with what is communicated on the packaging label) relatively often. Consumers with a stronger familiarity with bio-based products more often correctly dispose of compostable bio-based packages, but not recyclable bio-based packages, relative to fossil-based packages. Thus, although mainly compostable bio-based plastic packages have strong environmental appeal to consumers, paradoxically this does not translate in the proper disposal actions to fully capitalize on the environmental benefits that bio-based packages can actually deliver. Increasing consumers' bio-based product familiarity might be an avenue to increase the levels of sustainable disposal.