The success in computer courses is influenced by the levels of students' beliefs in their computer abilities (computer self-efficacy). Low level of computer self-efficacy (CSE) may affect to student's attention, engagement, and achievement in computer courses. Teacher feedback is one of the important factors helping students boost their CSE. The interaction with teachers influences students' intrinsic motivation and computer abilities. This study was to explore the influence of teachers' feedback in the computer classroom environment. The different types of teachers' feedback affect the different levels of students' CSE. An individual computer project was given to students. Data collection with pre-test and post-test design was used to capture students' changing perceptions of learning at the beginning and end of the computer course. The final sample was 105 high-school students in Thailand. A survey measured 8 items of abilities feedback, 5 items for general praise, 9 items for negative feedback, 5 items for CSE, and 24 items for SE Sources. Results from regression analysis revealed that SE source of social persuasions influenced by the ability feedback, along with general praise, and negative feedback respectively was the strongest predictor to predict students' CSE. The result highlighted not only teacher feedback can help students strengthen their CSE but also link with students' psychological Index Terms-Computer classroom, computer self-efficacy, needs in a computer classroom. feedback, self-efficacy source.