Nursing education is a process of theoretical knowledge and practical techniques needed by nursing students. Students who do not have previous practical experience are at risk of experiencing a mental workload, which can impact achievement, health, mental/emotional, social aspects, communication, and quality of life. This study aims to develop mental measurement workload in nursing students during clinical learning. Use mixed methods to combine or associate qualitative and quantitative data in 2021, with 596 participants from four vertical hospitals on the island of Java, Indonesia. Data analysis using Explorative Factor Analysis. The development process includes collecting quantitative and qualitative data, analyzing data results, making instruments, managing sample and population needs, validity and reliability testing instruments, modelling, and pilot projects and development. The results of measuring the student measuring instrument before the interaction obtained a value of 97.4% with a value of α = 0.993 (α> 0.7). The validity and reliability tests on the observation questionnaire consisted of 6 test results, namely before and during the interaction, which consisted of the orientation, identification, exploration, and resolution stages, then after interaction with the results of the validity and reliability tests in each phase had a Cronbach value> 0.7. The analysis with multiple regression, namely CFA analysis of the Lisrel program, obtained eigenvalue> 1, p-value> 0.5, and RMSEA <0.08. Our findings highlight that the developed instrument has a significant effectiveness value for measuring the mental workload of nursing students during clinical learning.