Mobile health (mHealth) literacy refers to the ability of individuals to seek, find, understand, and evaluate health information accessed via mobile devices. In Thailand, an assessment of mobile health literacy among the working-age population (25-59 years old) across the country is still needed to gain a better understanding of the current landscape of this concept as well as to create strategies for improvement. As a result, this study aimed 1) to assess mHealth literacy among the Thai working-age population, 2) to investigate differences in mHealth literacy among the Thai working-age population classified by demographic variables, and 3) to identify the predictive factors affecting mHealth literacy among the Thai working-age population. Cross-sectional survey research was conducted in this study with samples consisting of 600 working-age individuals derived from six regions across the country. Respondents were randomly selected using a multi-stage sampling method. Data were collected by a self-administered questionnaire. Mean, SD, t-test, One-Way ANOVA, and multiple regression analysis [MRA] were used for data analysis at a .05 level of significance. The results found that 1) the samples showed a high level of mHealth literacy (Mean = 4.32, SD = 0.58) 2), differences in mHealth literacy level were classified by gender, age, income, education, and region, and 3) perceived behavioral control, attitudes, and subjective norms were factors significantly affecting mHealth literacy. These findings can be used to plan and develop strategies for improving mHealth literacy among the Thai working-age population more effectively.