This paper examines the design and development process of a Hybrid network technology-enhanced language learning (HybridNTELL) model and evaluates its effectiveness. The model is grounded in a Vygotsky-inspired social constructivism approach to foreign language learning. The concepts of Zone of Proximal Development (ZPD) and Mediation underlie the model design framework, generating interactive content-based instruction in a community of practice. The aim of the HybridNTELL model is to foster the EFL learner autonomy required to live and work in a 21st century knowledge-based community. Four dimensions of autonomy were formulated based on literature on social constructivist theory and the current thinking on learner autonomy. The four interactive dimensions were used to inform four different types of task design: reactive-interdependence, reactive-independence, proactive-interdependence and proactive-independence which are the key components of the HybridNTELL model. Two platforms for applying the model in an EFL context are asynchronous online communication on a discussion board and synchronous face-to-face communication in the classroom. The use of two specific platforms complementary creates a hybrid learning environment. To evaluate the model?s effectiveness, 90 first year Chulalongkorn University students were recruited in experiment by stratified random sampling method. The students participated in a HybridNTELL environment during a one-semester English foundation course which is compulsory for non-English major students. Findings suggest that the HybridNTELL model yields positive effects on EFL learning autonomy development based on an assessment of the improvement in students? English proficiency, achievement test scores, curriculum-based holistic performance development and objective language development.