English language programmes provide established pathways for international students seeking university admission in countries such as Australia and the United Kingdom. In order to refer international applicants to appropriate levels and durations of English language support prior to matriculation into their main course of study, pathway providers need effective and efficient language assessment tools. This report evaluates the effectiveness of an online vocabulary knowledge test as an index of English proficiency for university English pathway programme applicants (N = 177). The Timed Yes/No (TYN) test measures vocabulary recognition size and speed in a time- and resource-effective format. Test results were correlated with performance on a comprehensive placement test consisting of speaking, writing, reading and listening components. The predictive validity of word recognition accuracy (a proxy for size) and response time (a measure of efficiency) for placement test outcomes were examined independently and in combination. The TYN test scores' sensitivity at predicting comprehensive placement test scores were assessed using a cut-score analysis resulting in an identification accuracy rate ranging from 76 to 86% for five critical band scores. The potential use of the online vocabulary-screening test for measuring international students' English language proficiency is discussed in terms of reliability, validity, speed, usability and cost-effectiveness in onsite and offshore testing conditions.