The importance of age in language learning has been debated for a long time. The general assumption is that age plays a positive role in facilitating language learning and attaining native-like competence. This paper is concerned mainly with investigating the role which age plays in mastering syntax/morphology and phonology in the process of language learning. It also pays some attention to the effects of age on the route or the way and the rate or the amount of learning. Studies carried out earlier on the effects of age are reviewed in this paper. It reviews how age affects learning and what aspects of language it affects focusing on syntax/ morphology and phonology. It is concluded that age mainly affects phonology. That is, starting to learn a language early leads to native-like pronunciation. However, it is found that an early start is not an advantage for learning syntax and morphology. It is recommended that language be introduced early in curriculums so learners make more benefit from early start to master the target language.