This study aims to study the extent to which the application of Socio-Scientific Issues (SSI) combined with the Problem-Based Learning (PBL) model is able to improve students’ abilities in the field of 21st-century skills. The method used is a literature review study by analyzing 25 research articles, consisting of 15 articles from national journals and 10 articles from international journals. The results of the study indicate that SSI-based learning has a positive impact on improving scientific literacy, environmental literacy, critical thinking, problem solving, decision making, and communication skills. The integration of SSI in project-based learning has been shown to increase enthusiasm for learning, make students more active, and help them understand environmental issues. SSI-based learning is a good way to train the skills needed in the 21st century.