It is important to work on verbal mathematical problem-solving skills, which is one of the high-level skills with which students have difficulty. Supporting problems with visuals has been suggested by mathematics educators to develop this skill. This study examined the effect of the visualization of mathematical problems on the problem-solving performance of primary school first grade students. The study group consisted of 41 students attending first grade in a public primary school located in a low socio-economic status region of Istanbul. Semi-structured individual interviews were conducted with 8 students. Problem-solving questions developed by the researchers were used for pretest and post-test, the results of which were analysed using the Wilcoxon Signed-Ranks test. For the experimental process, the Visually Supported Problem-Solving Worksheet was used as a data collection tool. Students' views on the implementation were analysed using a content analysis method. The results indicate that the problem-solving worksheet supported with visuals was effective in improving the mathematical problem-solving performance of the students. The majority of the students stated that the implementation contributed to improving their performance and their satisfaction.