Objectives: In 2010, 275 million metric tons (MT) of plastic waste was generated in 192 coastal countries, of which 4.8 to 12.7 million MT entered the ocean (Jambeck, et al., 2015). The aim of this research project was to experimentally examine differences in Pro-Environmental Plastic Use through framing manipulations on messages (loss-frame and gain-frame) and implementation intentions (autonomy-frame and heteronomy-frame). Method: One hundred and forty-five participants (82% female) completed two online questionnaires involving two manipulations; firstly to read a message (gain-frame vs. loss-frame), and secondly to implement behavioural plans to reduce plastic use (autonomy-frame vs. heteronomy-frame vs. control group). The questionnaires measured Pro-Environmental Plastic Use, Intentions, Attitudes, Perceived Self-Efficacy, Consideration of Future Consequences (CFC), and the New Ecological Paradigm (NEP). This study employed a 2 (message framing: loss, gain)  3 (implementation intention frame: control, autonomy, heteronomy) between-subjects experimental design. Results: Four ANCOVAs found no main effects found for message framing (loss, gain). A significant main effect for implementation intention on Pro-Environmental Plastic Use was found, such that those in the heteronomy-framed implementation intention reported lower Pro-Environmental Plastic Use than those in the autonomy-frame and those in the control group. There were no significant differences found for implementation intention on Intentions, Attitudes, but was reaching significance for Perceived Self-Efficacy. Conclusion: This study has produced novel theoretical and practical implications for pro-environmentalism. The study’s strengths, limitations, and directions for future research are discussed.