Language mindsets - beliefs about whether language learning ability is immutable or malleable - have received much attention in psychology and education research due to their vital role in learners’ motivation and achievement. Despite this, research on the language mindsets regarding specific language skills has been under-explored. This study aims to fill this gap by focusing on mindsets about EFL speaking of Vietnamese tertiary students and examining the role of demographic factors in their mindsets. The study employed the mixed-methods approach using a language mindset survey and a semi-structured interview. 226 EFL students at a public university were recruited, using a convenient sampling technique, to respond to the survey. Purposive sampling was also employed for the interviews. Findings revealed that most students endorsed a growth mindset about EFL speaking while over one-third held a mixed mindset. Female students endorsed greater growth mindsets about EFL speaking than male counterparts, whereas more male students demonstrated a mixed mindset than did female students. However, there was no statistical relation between the language mindsets and demographic variables. The study implies that foreign language pedagogy should foster growth mindsets while cultivating mixed mindsets to promote EFL speaking among students.