Abstract: The aim of the study is to figure out the relationship between morphological awareness and vocabulary size. More specifically, the primary purpose of the current study concerned whether English-majored students’ morphological awareness existed the correlation with their vocabulary size. There were two tests used in this study. The Vocabulary Levels Test was adapted from Al Farsi (2008), cited in the Vocabulary Levels Test (Nation, 2001). The test was to measuring English-majored students’ ability to memorize learned English vocabulary. In terms of a modified version of the Morphological Awareness Test (McBride-Change et al, 2005) was also adapted from Al Farsi (2008), which was used to determine vocabulary size. Besides, Independent Samples Test was run by the software to investigate if there was the difference of the tests’ results between male participants and female participants. Participants in this study were senior English studies majors at Nam Can Tho University. One hundred and seventeen students were chosen at random to participate in this study. The participants varied in age from twenty-two to twenty-six. They were all native speakers of Vietnamese who had studied English as a foreign language for at least 10 years. There were seventy-five female participants and forty-two male participants. They were tested at their university during the second semester of the 2022–2023 school year. The results showed that English-majored students’ morphological awareness at Nam Can Tho University had the average correlation with their vocabulary size. In addition, there was no significant difference between male and female students.