The research literature on the topic of "spatial ability" reveals that it has a major influence on achievement in the fields of science, technology, engineering and mathematics. Additionally, previous studies indicate the existence of a gender gap in spatial ability in favour of males. Mental rotation, one subskill of spatial ability, is an area in which gender differences are greater. At the same time, educational robotics is seen as one of the more promising technologies in educational contexts for the future. We conducted a quasi-experimental study with 142 seven- and eight-year-old students aimed at analysing whether robotics-based instruction may produce greater learning gains on mental rotation abilities compared to traditional instruction. The intervention was developed in the context of map-reading tasks, which are part of the curricular content in Mathematics and Social Sciences at this age. The results showed that for males, the robotics-based instruction promoted a significantly greater improvement in students' mental rotation abilities compared to the control group. By contrast, no significant differences were observed for females. Although this study provides empirical evidence of the potential of robotics-based instruction, future studies need to deeply analyse the existence of gender differences in the learning gains obtained through educational robotics.