Previous studies revealed that many students cannot perform well when it comes to word problem-solving questions. There are various problem-solving strategies that can be applied to help students to overcome the problem. Visualisation techniques in learning have been used to help students enhance their conceptual understanding of the mathematical problem-solving and the use of bar model visualisation technique is one of the strategies. This study aims to investigate students' achievement in mathematical problem-solving after applying the Bar Model and to explore students' experiences while applying the technique. This study employed a preexperimental design of the quantitative research. There were 32 participants of year three students. The instrument used in this research consists of questions of pre-test and post-test and a semi-structured interview. Data were analysed using SPSS 20.0 software and thematic analysis. The test results showed that there is a significant difference in participants' mathematical problem-solving achievement. The analysis of semi-structured interview transcripts revealed that level of understanding and motivation influence students' performance. Findings of this study showed that students perform better after the implementation of the Bar Model in mathematical problem-solving. This study can provide an alternative or guidance for teachers to improve students' mathematical problem-solving skills.