This research aims to design and validate the contents of the mathematical creative problem-solving (MCPS) instrument to measure creative problem-solving skills. This instrument consists of four aspects, each with related items representing latent variables for promoting students’ MCPS. An instrument construct that contains aspects of divergent and convergent thinking is presented. The stimulus provided is real problems in everyday life (real-world situations) with tiered levels of structure of the observed learning outcome (SOLO) taxonomy. The question structure developed is in the form of near-transfer and far-transfer questions. The content validity process is presented by seven expert validators experienced in mathematics, mathematics education, and measurement. The level of agreement between expert assessments is determined using the Aiken formula. Aiken coefficient for all items is above the good threshold. The instrument developed has demonstrated strong content validity and is recommended for measuring MCPS skills of junior high school students.