Motivation and success in computer-science courses are influenced by the strength of students' self-efficacy (SE) beliefs in their learning abilities. Students with weak SE may struggle to be successful in a computer-science course. This study investigated the factors that enhance or impede the computer self-efficacy (CSE) of computer-science students. Data collection involved a survey of 524 undergraduate computer-science students from 10 Thai universities. The survey measured four items of CSE, 13 items pertaining to the classroom learning environment (CLE), and 14 items related to information sources of SE. Results revealed that perceptions of a CLE with autonomy, meaningfulness, and involvement were positively associated with strong CSE. In addition, perceptions of social persuasions such as meaningful and encouraging feedback or judgment from influential people demonstrated a statistically positive relationship with CSE. Perceptions of vicarious experiences whereby students determine and compare their own abilities with observational experiences of role models also demonstrated a statistically positive relationship with CSE. Perceived physiological and affective states such as anxiety and stress demonstrated a negative influence CSE. Implications for practice relate to students' perceptions of autonomous learning, the value of positive feedback, students' input into learning content and activities, role models for students and observation of how peers perform tasks better or worse.