The basic tenet of constructivism is that learners construct their knowledge on their own by associating new with prior information. The significance of the learner’s interaction with his/her social and physical environment is here of great importance; the learner is at the center of the learning process while the tutor is seen as a facilitator, a guide. Considering the paradigm shift in education and language learning, the assumptions of the constructivist philosophy encourage the use of computers in second language acquisition. Computer technology is capable of providing the context for collaboration and social interaction in which learners will construct the knowledge of the target language on their own by being engaged in meaningful activities. Moreover, computers allow learners to interact not only with the learning materials but also with other people. The combination of the social and individual aspect is best expressed by social constructivism. Placing language learning in a socio-cognitive context, we will approach second language acquisition from a social constructivist perspective and indicate the value of such an approach for the design and evaluation of Computer Applications in Second Language Acquisition (CASLA). Firstly, an overview of constructivism as a theory of learning is required in order to make clear the basic assumptions of the constructivist theory. Secondly, the focus is placed on social constructivism which is examined in relation to second language acquisition. This in tandem exploration will lead us to provide a framework which integrates all four language skills in a general theoretical framework of social interaction and shows how social constructivism can promote second language acquisition. Finally, one type of on-line application such as WebQuest, which is best developed in project-driven language learning, will be provided as a potential example of good practice in approaching Computer Applications in Second Language Learning through a social constructivist perspective.