English Learners may struggle when learning science if their cultural and linguistic needs are unmet. The Collaborative Online Projects for English Language Learners in Science project was created to assist English learners’ construction of science knowledge, facilitate academic English acquisition, and improve science learning. The project is a freely available, online project-based, bilingual instructional web-site designed for English learners of Hispanic origin. The project website contains two units: Let’s Help Our Environment and What Your Body Needs. To create these collaborative online projects, two constructivist approaches were combined: The Cognitive-Affective Theory of Learning with Media and Project-Based Learning. These approaches to science education were used as the basis for culturally and linguistically relevant science instruction, which was delivered within a collabora-tive, online instructional platform. Using a case study design, two teachers demonstrated implementation of the project with fidelity, and students showed statistically significant gains in science content assessments. The Collaborative Online Projects for English Language Learners in Science project provides educators with a strong model for creating instructional materials that support English learners’ science learning by combining culturally-relevant, constructivist, collaborative projects using online, multimedia technology.