this study to develop and validate a text-based chatbot system and determine its effectiveness, focusing on grade nine students' least learned English competencies in one of the public schools in Magalang, Pampanga, during 2020-2021. This study utilized a multiple method research design since it combined two research designs, specifically developmental and quasi-experimental. This study aimed to evaluate the validity of the material using quantifiable and numerical data. Furthermore, the researcher used an adapted research instrument and a validated teacher-made pre-test and post-test, focusing the least learned competencies on thirty participants. Also, the researcher used one group pre-test-post-test. Moreover, the instruments were used as primary data collection tools, statistically treated, and analyzed using the mean, standard deviation, and paired T-test. The findings revealed that the least learned competencies were under the grammar awareness and writing composition domains. Specifically, the - least learned competencies were using adverbs in narration, recognizing the use of verbals, and types and features of a short prose and play synopsis. Also, the post-test scores' standard deviation was closer to the mean. Moreover, the results showed that the pre-test scores of the participants were fairly satisfactory, whereas the post-test scores were outstanding after using the text-based chatbot. The intervention of the text-based chatbot revealed improvements in the participants' test scores; thus, the researcher recommends using the text-based chatbot as a supplementary learning material focusing on the least learned competencies under the K to 12 Curriculum Guide. Key Words: chatbot, least learned competencies, self-regulated learning, text-based.