Learning a new language cannot be separated from the vocabulary. Vocabulary can be defined in many ways. Knowing vocabulary in English is also very important in the process of learning English because if we comprehend the vocabulary, we can easily use the words we want to convey. The researcher is interested in conducting research about autonomous learners, Duolingo, and himself as participants. This research is aimed to investigate the undergraduate student as self-directed learners with the assistance of a language learning application that is Duolingo. The methodology employed to investigate the self-directed student experience on vocabulary language learning by implementing Duolingo among undergraduate students. Duolingo offers several features that can support self-regulated vocabulary learning. Its gamified interface provides an engaging and interactive learning environment, motivating researcher consistently engage in vocabulary learning activities. In conclusion, self-regulated vocabulary learning using Duolingo present a promising result for second language acquisition. By employing narrative inquiry, the researcher gained a deeper understanding of motivation, challenges in using Duolingo for vocabulary learning from his own experiences. The findings from this research can have implications for language learning pedagogy. By exploring learner’s experience with self-regulated vocabulary learning using Duolingo, we can gain insight into the effectiveness of such technological tools in promoting vocabulary acquisition.