The ability to effectively communicate at work, home, and in life is probably one of the most important sets of skills a person needs. English as a tool of communication as standardized by International Maritime Organization (IMO), needs to be implemented in order to improve learning needs, cognitive and affective abilities, for self-confidence is considered to be a significant factor which influences the learners’ language performance. The purpose of this study is to find out the cadets’ level of self-confidence category in delivering marine communication on board and the causes of the level of the self-confidence. The research uses descriptive qualitative design. The participants of the research is deck and engine cadets semester IV from Politeknik Ilmu Pelayaran Makassar who were scheduled for practicing on the training ship. The variable of this study is the cadets’ self-confidence in delivering marine communication on board simulation. The data are collected through questionnaire, observational checklist and interview related to self-confidence of the cadets in delivering marine communication on board Training Ship Sultan Hasanuddin. The data from questionnaires were analyzed by scoring the positive and negative statement into Likert’s scale (strongly agree, agree, undecided, disagree, strongly disagree) and classified the level of sel-confidence by the score scale to determine The High Self-Confidence, Moderate Self-Confidence, and Low Self-Confidence. The results of the study show that there are three levels of cadets’ self-confidence in delivering marine communication on board simulation, they are categorized as high, moderate and low self-confidence. The cadets high self-confidence is caused by the feeling of excited to do simulation. Moderate self-confidence of cadets is caused by high motivation in English, but could not engage the indicators of people with self-confidence. However, Low self-confidence of cadets are caused by mispronunciation and unfamiliarity situation on board.