The emergence of generative artificial intelligence has marked a significant change in the landscape of educational technology and have shown importance in various tasks. Existing literatures widely explore the application of AI technologies in education however there is less attention given as to how pre-service science teachers utilize generative AI tools on their practicum teaching. Thus, there is a need to investigate the use of generative AI tools by pre-service science teachers on their practicum. An explanatory sequential design was used in this study wherein the quantitative data gathered from 87 respondents were analyzed using descriptive statistics (mean and standard deviation). Whereas, thematic analysis was used to analyze the qualitative data. The results revealed that most of the pre-service science teachers used ChatGPT, 84 (96.60%) out of 87 respondents. In addition, the pre-service science teachers ‘agree’ with the utilization of generative AI tools on practicum performance such as in lesson planning (M = 4.04, SD = 1.05), instructional skills (M = 3.90, SD = 1.11), classroom management (M = 3.50, SD = 1.19), and personal and social qualities (M = 3.68, SD = 1.15). Moreover, for the qualitative results specifically influences of generative AI tools and suggestions of pre-service science teachers, the following themes emerged: (1) makes work easier and faster, (2) improves practicum performance, and (3) develops reflective teaching practices and (1) premium accounts for pre-service science teachers, (2) clear and specific prompts, (3) generative AI tools as supplementary aid, and (4) responsible and ethical use of AI tools, respectively. These findings highlight the need to equip pre-service science teachers with the adequate knowledge and skills to utilize generative AI tools responsibly, ethically, and effectively on their practicum performance. This study recommends that concerned institutions should implement programs on how generative AI tools can be integrated effectively into practicum.