The purpose of this study was to explore the use and effects of AI PengTalk on primary English learners’ vocabulary knowledge and affective domains. The research was carried out with one class of sixth graders (a total of 17 students) from a primary school. Learning English based on AI PengTalk was conducted over fifteen weeks. Vocabulary knowledge tests, affective domain tests, a student questionnaire, and a teacher's observation journal were used to collect data. The results were analyzed using quantitative and qualitative methods. Paired t-tests using SPSS were used to analyze quantitative data, and the questionnaire and observation journal analysis were used to analyze qualitative data. It was found that learning English using AI Peng Talk had a positive effect on primary English learners’ vocabulary knowledge and affective domains. In addition, it is determined that AI PengTalk increases primary English vocabulary knowledge and affective domains such as attitude, interest, belief, and expectation.