This study focuses on a technological tool known as the Mobileassisted Mind Mapping Technique (MAMMAT). This tool was designed and developed as a mobile application to deliver essential course contents employing online mind mapping to support argumentative writing skill performance. The primary purpose of this study was to determine the effects of MAMMAT on English as a Second Language (ESL) university students in Malaysia. The participants of this study were 45 ESL university students from two lecture groups at a public university campus in Malaysia. The study employed a quasiexperimental research design. The experimental group was taught with the MAMMAT while the control group was taught using the conventional method. The pre-test and post-test scores were analyzed through the analysis of covariance (ANCOVA). Based on the ANCOVA results, the mean score of post-tests for the MAMMAT on the experimental group was higher than the mean of post-tests on the control group in terms of argumentative writing performance. Therefore, the MAMMAT was found to be effective in enhancing the argumentative writing performance of ESL university students. MAMMAT supports and enhances ESL university students' argumentative writing skills performance through innovative use of mobile technology, and this technique shows potential not just for second language learners of English in Malaysia but in other countries as well.