We examined how young adults processed ecolabels (i.e. environmental warning labels), specifically by investigating how different warning message conditions and issue-relevant factors influenced the effectiveness of environmental warning messages. Findings from a 3 (message context formats: ads vs. positive PSAs vs. negative PSAs) x 3 (product categories: conservation vs. recycling vs. eco-friendly) mixed within- and between-subjects experimental design indicated that the effectiveness of ecolabels, assessed via message recall, message recognition, attitudes, and behavioral changes, was influenced by various issue-relevant determinants, as well as message context formats and context-induced moods. We also found that these predictors exhibited distinct patterns of influences for different types of environment-friendly products. Theoretical implications, as well as empirical suggestions for environmental communication professionals and policymakers to enhance the effectiveness of ecolabels and young adults’ awareness of environmental threats, were discussed.