AbstractThis study examines the effectiveness of the Duolingo ABC application in improving English vocabulary mastery among early childhood learners at 'Aisyiyah Bustanul Athfal Merduati Kindergarten in Banda Aceh, Indonesia. Using a true experimental design with a control group framework and pre-tests and post-tests, this study involved 32 kindergarten students divided into two groups: the experimental class (B-1, n=16) and the control class (B-2, n=16). The experimental group received vocabulary instruction using the Duolingo ABC application as a digital learning medium, while the control group was taught through conventional visual aids, namely hand puppets and pictures. The learning materials covered two main themes: basic vocabulary (the alphabet, names of fruits, and names of animals) and basic sentences (nominal sentences and verbal sentences), which were implemented over ten sessions. Data were analyzed using descriptive statistics and paired-sample t-tests in SPSS. The results showed that the experimental group achieved a significantly higher average post-test score (M = 96.88; SD = 4.79) than the control group (M = 78.75; SD = 7.19), with a statistically significant difference (Sig. 2-tailed = 0.000; p 0.05). These findings demonstrate that integrating the Duolingo ABC app as a technology-based learning tool significantly improves students' English vocabulary mastery and promotes more consistent learning outcomes among learners. This study provides empirical evidence supporting the implementation of gamification-based digital learning apps in early childhood English education.Keywords: Vocabulary, Duolingo ABC, Apps, Early Childhood, English Learning.