The aim of this study was to evaluate attitudes towards and achievement in science of Form 3 students studying in single-sex and coeducational schools in Brunei. The results demonstrated significant differences in attitudes towards and achievement in science of male and female students in single-sex schools and students in coeducational schools. These differences were at moderate level. In single-sex schools, the girls achieved moderately better in science than the boys despite their attitudes were only marginally better than the boys. However, there were no gender differences in attitudes towards and achievement in science of students in coeducational schools. The attitudes towards and achievement in science of girls in single-sex schools were moderately better than those of girls in coeducational schools. Whereas the attitudes towards and achievement in science of boys in single-sex schools were only marginally better than the boys in coeducational schools. However, further research to investigate (a) if these differences are repeated at other levels as well as in other subjects, and (b) the extent to which school type contributed towards these differences is recommended.