Recently, a new cognitive style approach was introduced, which refers to two types of visualizers. This approach is based on neuropsychological evidence and neuroimaging results, which suggest the existence of two distinct imagery subsystems, the object and the spatial imagery subsystems. The goal of the study was twofold: first to examine a possible relationship between this new cognitive style approach and achievement in number sense and algebraic reasoning tasks, and second to explore a possible relationship between the strategies used in solving the aforementioned tasks and cognitive styles. A mathematical test on number sense and algebraic reasoning and the self-report Object-Spatial Imagery and Verbal cognitive style questionnaire were administrated to 83 prospective school teachers (PSTs). The results indicated that spatial imagery, in contrast to the object imagery and verbal cognitive styles, is related to achievement in number sense and algebraic reasoning. In addition to this, the results revealed that the higher the PSTs' tendency towards spatial imagery cognitive style, the more conceptual and flexible strategies they employ in algebraic reasoning and number sense tasks.