Consideration set size is an important factor deciding consumer's choice. This study explores the determinants of consumer's choice through consideration set size. Six factors are expected to affect consideration set size including perceived quality, perceived price, knowledge, convenience orientation, perceived convenience and variety seeking. Structural equation modeling is applied to analyze data sample of 400 consumers in Nha Trang. The statistical testing confirms the reliability and validity of all constructs and measurement model can be representative for data. Five variables except perceived convenience are found to be significantly affects consideration set size. Perceived price is the most important factor. The results imply important policies for Vietnamese seafood companies to compete in domestic market.