ChatGPT has gained popularity among Philippine educational institutions due to its versatility and usefulness in academic activities. However, educators have raised concerns about the ethical issues, academic dishonesty, and technology dependence associated with its use. This study aimed to develop and validate an instrument called KAP-CQ39 that assesses the knowledge, attitudes, and practices of preservice teachers regarding the use of ChatGPT. The study involved 4 experts, 12 independent evaluators, and 206 preservice teachers. The instrument underwent a series of assessments to establish quality, validity, and reliability, resulting in the final version of KAP-CQ39. Results showed that KAP-CQ39 has acceptable content validity (CVR and CVI values>0.78), face validity (IS>1.5), construct validity (chi-squared value of 897.564, df=577, p<0.001), and internal consistency (overall Cronbach coefficient=0.91). This proved that KAP-CQ39 can be a valuable tool for assessing the impact of ChatGPT on the Philippine educational system and can provide insights for educational policy makers regarding the use of artificial intelligence in education.