Microencapsulation technology has been used in a variety of fields including materials such as buildings, walls, industrial, medicine, and cosmetics. One of the most active research on microencapsulation is microstructure formation. Important properties of microcapsules such as releasing rate of active agent are depending on their microstructure. Same as the strength of bridges, skyscrapers, and buildings is characterized by their geometry, and the strength of microcapsules is also influenced by their microstructure. The effect of trioctylamine on the morphology of polystyrene microcapsules was investigated. The influence of trioctylamine was on both the inner and outer morphology of microcapsules. On outer morphology, two types which are smooth and crown were observed. Three types of inner morphology of microcapsules were classified. The inner morphologies are evenly spaced, clustered, and randomly spaced. The morphologies of the crown and evenly spaced were small in size.