Soft skills such as grit, self-control, and self-confidence have been shown to predict outcomes in school and in life. As such, their valid and reliable measurement is of substantial interest in educational research and policy circles. However, the vast majority of this research originates in Western countries; relatively little is known regarding the measurement of soft skills in developing country contexts and whether similar types of instruments can provide evidence of these skills. This paper presents a novel means of assessing grit, self-control, and self-confidence in rural Tanzania: through the use of scenario-based self-report questionnaires. Survey instruments were administered in three regions in Tanzania to 961 Standard 2 pupils. We found that scenario-based items provided valid and, in most cases, reliable estimates of the three tested soft skills. When comparing self-reported soft skills and reading ability, we found that both grit and self-control were significant predictors of reading and mathematics performance. After controlling for sex, region, and age, grit was found to have a stronger association with reading performance than socioeconomic status.