The purpose of the present study is to provide empirical evidence on the adaptation of the mathematics-related beliefs questionnaire (MRBQ) supplemented by info-communication technology-related items. Besides, we also investigate the relationship between their beliefs about mathematics and their ability in problem-solving mathematics. 234 grade eight students from five schools in Java, Indonesia, participated in this study. The questionnaire has appropriate reliability. To examine the validity of the questionnaire, factor analysis was applied, and regression analysis was conducted to explore students' beliefs and their relation to their performance. Factor analysis revealed a good fit of the model; therefore, confirming the validity of MRBQ in the Indonesian context. Descriptive statistics showed students' tendency to follow the nonrealistic approach when doing word problems. Regression analysis indicated the significant role of beliefs in mathematics predicting students' performance on mathematical word problems.