Language is at the core of Content and Language Integrated Learning (CLIL) programs along with culture, environment, content, and learning (Marsh, Maljers & Hartiala, 2001). Among other linguistic skills, writing has a unique role and purpose in that it acts as a bridge between content and language. Thus, it is crucial to reveal all aspects of the dichotomous relationship between writing skills and CLIL programs. In this respect, this study set out to conduct integrative research on the impact of CLIL programs on writing skills. Rather than a holistic approach, this study adopted a component analysis that emerged in the studies found, and the independent variables were refined to age and exposure duration. Before the data collection process, specific criteria were set for the studies: the studies would be empirical with a comparison group (CLIL vs Non-CLIL). The focus of the studies would be on the components of writing skills, and the studies would include the age of the participants and the exposure duration to CLIL. Within this framework, 15 studies were found, and the results were analysed. The results indicated that age is not a definite determiner in the overall writing production except for lexical complexity. Also, longitudinal exposure to CLIL is found to be slightly more effective than Non-Longitudinal studies. Similarly, lexical complexity was better-improved in a Non-CLIL setting for longitudinal studies.