A valid, reliable and practical instrument is needed to evaluatethe implementation of higher order thinking skills (HOTs) amongst teachers in primary schools. The purpose of this study was to assess the validity and reliability of an inventory in promoting HOTs. The inventory wasadapted from Nurasyikin (2016), Gulistan et. al(2016) and Gonzales and Fugan (2012). The instrumentin the form of questionnaire was distributed to a sample of 220 primary school teachers teaching Islamic education subject. The content validity was assessed by a group of experts, and the construct validity wasmeasured byanExploratory Factor Analysis. The reliability of the instrument wasmeasured by thealpha coefficient reliability or Cronbach Alpha. Results of Exploratory Factor Analysis suggestedthat 12 items neededto be removed due totheirnon-dimensionality as they hadmore or less equal loadings on several factors. The instrument developed yielded high values of internal consistency as reflected by the Cronbach alpha values. The final draft of the instrument contained 107 items which was consideredvalid and reliable. Even though the validity and reliability of the instrument werewithin the acceptable range, more data neededto be gathered with a bigger sample, and further analysis using an Item Response Theory (IRT) model could beused to explore deeper into the psychometric characteristics of the items
