Purpose: Distance universities are of great importance for establishing sustainability literacy, as they operate as multipliers for thousands of students. However, despite several advantages of e-learning environments compared to traditional class-teaching, there are still challenges regarding suitable e-learning tools and didactical models. The purpose of this paper is to evaluate the effectiveness of several e-learning tools on students' knowledge and skills growth and to compare two learning paths, synchronous vs asynchronous, exploring how each affects the level of students' knowledge achievement and skills acquisition. Design/methodology/approach: The empirical analysis is based on an online course "Participatory processes in environmental politics". International MSc and PhD students who enrolled in the course were from FernUniversität in Hagen (Germany) and Aberta University (Portugal). The course was designed as the flipped classroom, applying different e-learning tools and activities, some synchronous and others asynchronous. A pre- and post-evaluation questionnaire was applied to evaluate students' knowledge and skills. Descriptive statistical analyses were carried out on this data. Findings: Results showed that in the synchronous group, knowledge about theoretical approaches to citizen participation and sustainable environmental governance improved to a greater extent, whereas the asynchronous group showed greater improvement in nearly all skills related to intercultural communication and e-learning. Also, in the synchronous path, students enhanced their knowledge on "research application" to a greater extent. Originality/value: Evaluating the effectiveness of different e-learning tools on students' sustainability knowledge and information and communication technologies skills is a fundamental issue. The study discusses these issues, contributing to enhancing the use of adequate and grounded e-learning models on sustainable development in higher education.