Mathematical thinking beliefs are a significant element in supporting teachers' practices of learning and teaching school mathematics. Most prior researches on mathematics beliefs have focused on teachers' beliefs about learning and teaching mathematics in general. This research aimed to validate a Mathematical Thinking Belief instruments (MTB). The instrument was distributed to 523 mathematics teachers in Omani public schools. These teachers were asked to write their opinion in an instrument with a 5-point Likert scale. Exploratory factor analysis and confirmatory factor analysis have been applied to test the MTB using AMOS 25.0. All constructs show acceptable internal consistency reliability. The model meet a good model fit for the mathematical thinking beliefs measurement model through different fit index tests such as CMINDF, CFI, GFI, SRMR, RMSEA, and TLI. The results show that all indices of fit criteria were achieved. It is also indicated that acceptable validity, construct reliability and variance extracted values.