Plastics have much to offer as a modern convenience, but lack of responsible plastic waste management habits can lead to potentially harmful environmental effects. Past environmental initiatives revealed a lack of understanding about youth attitudes towards pro-environmental issues. [minus]plastic, an online public environmental promotional campaign, encouraged Singaporean youth to recognize the importance of, adopt positive attitudes towards and subsequently adopt the practice of responsible plastic management. We propose the Temporal Incentives Model of Social Influence, based on Prochaska and DiClemente's stages of change model, to guide social campaign design. A pre-post quantitative research design showed that the pre-contemplation, contemplation and preparation stages progressed significantly after the campaign. The findings suggest that stimuli incorporating specialized information and small action steps allow migration to successive stages. With the strong presence of internet culture among Singaporean youth, the online medium was found effective in altering the attitudes of the campaign target audience, while exposure to the campaign messages proved useful in encouraging environmental learning among youth. (Contains 3 figures and 1 table.)