The objective of this study was to validate a bilingual Spanish-English version of the Vocabulary Size Test (VST) considering its potential use as a discriminator between learners in terms of language competence. This version was designed based on the two forms available on one of the creators’ websites as well as considering practices recommended regarding the elimination of cognates and loans. A one-way ANOVA test was used to confirm the test’s capacity to discriminate among learners of different linguistic competence. Additionally, Principal Axis Factoring (PAF) was conducted to revise the existence of only one underlying variable. As a result of this study, a VST version for Spanish speakers consisting of 9 vocabulary frequency levels is shared. This version is in line with validation standards put forward in previous research. It is expected that this instrument will help future studies that seek to measure Spanish speakers’ competence in English as a foreign or second language without having to deal with the interference of other intervening factors.
