<![CDATA[Vocabulary mastery is one of the fundamental components of English as a Foreign Language (EFL) learning because it provides the foundation for learners to comprehend meaning, process input, and communicate effectively. Preliminary observation conducted at MI Ma'arif NU Sukolilo revealed that fifth-grade students still experienced considerable difficulty in recognizing, remembering, and understanding English vocabulary, a condition that potentially hinders their overall language development if left unaddressed. This study aimed to examine the effectiveness of TikTok English Video Quiz combined with Modified Card Response (MCR) in improving elementary students' vocabulary mastery. A quantitative approach was employed using a pre-experimental one-group pre-test and post-test design. The participants consisted of 24 fifth-grade students selected through purposive sampling. The research instrument was a 20-item vocabulary test administered before and after a three-session treatment in which students watched TikTok English Video Quiz videos and responded actively using colored Modified Card Response cards. Data were analyzed through descriptive statistics, the Shapiro–Wilk normality test, a paired-samples t-test, and Cohen's d effect size calculation using JAMOVI software. The results showed that the mean score increased from 58.3 in the pre-test to 87.5 in the post-test. The paired-samples t-test indicated a statistically significant difference between the two measurements, t(23) = -10.7, p < .001, and the effect size analysis yielded Cohen's d = 2.18, categorized as a very large effect. These findings indicate that the integration of audiovisual digital media with an active, kinesthetic response technique can substantially improve young learners' vocabulary mastery. The study offers empirical support and practical guidance for English teachers seeking to design more interactive, technology-assisted vocabulary instruction for elementary school students.]]>
