Misinformation about GMOs (genetically modified organisms) circulated on social media has negatively impacted people’s beliefs and behaviors. This study explores whether and how the information element of online news can improve public attitudes toward controversial issues such as GMOs. For this purpose, a 2 (gain vs. loss frames) x 2 (one-sided vs. two-sided messages) experimental design is adopted. The results of ANCOVA show that those exposed to two-sided messages showed greater levels of GMO acceptance compared with those exposed to one-sided messages. A significant interaction effect on GMO acceptance was also found, demonstrating that a two-sided message focusing on the gain frame showed the highest levels of GMO acceptance. In addition, the effects of message sidedness and gain-loss frames on GMO attitudes are mediated by psychological reactance. Specifically, two-sided messages, compared to one-sided messages, led to lower GMO risk perceptions and higher GMO acceptance by reducing psychological reactance. Furthermore, compared to loss-framed messages, gain-framed messages decreased GMO risk perceptions and increased GMO acceptance by lowering participants’ psychological reactance. These results can provide a deeper understanding of the mechanism by which news messages might influence individuals’ acceptance of scientific information through activating psychological reactance.