This thesis aims to investigate the relationship between pupils' self-confidence in their writing ability and their ability to use accurate grammar. The study is based on Albert Bandura's Self- efficacy theory on individuals' self-confidence and their performance. A quantitative research methodology with a correlation analysis was used for this study. The study included a total of 63 participants from a high school in order to capture the perception and attitudes of the participants. The questionnaire consisted of 19 questions divided into two categories, one with questions about grammar and one about general writing. The results analyzed with Pearson's correlation coefficient can establish the relationship between pupils' self-efficacy in writing with their grammatical proficiency. The results show a moderate positive correlation between the pupils' confidence in their competence in writing and their grammatical proficiency, which confirms Bandura's theory. The restricted sample size affects this study as it cannot be generalized to a larger population, therefore this study cannot claim to make conclusive findings. However, the survey can serve as a basis for further research on the topic with a more widened sample.