<sec> <title>BACKGROUND</title> <p>Due to the impact of the coronavirus disease 2019 (COVID-19) pandemic, work environments and systems, as well as occupational health measures or activities that fall within our research field, are constantly changing. We consider it necessary to assess the impact of these changes on the physical and mental health of workers.</p> </sec> <sec> <title>OBJECTIVE</title> <p>To assess how occupational health measures affect the health of workers, we conducted a baseline longitudinal Internet-based survey among Japanese workers in October 2021, and additionally scheduled two follow-up surveys for 2022 and 2023.</p> </sec> <sec> <title>METHODS</title> <p>This survey is a prospective cohort study conducted online among Internet monitors. The baseline survey was conducted from October 1 to 7, 2021. The study targeted those who were working and between the ages of 20 and 69 years. Regarding sampling plan, 5111 respondents who passed the screening survey and proceeded to the main survey were enrolled according to collection units organized by both sex and age group. For the screening and main surveys, the questionnaire consisted of 9 and 33 items, with 9 and 55 total number of questions, respectively. We performed consistency and completeness checks after the questionnaires were submitted. We compared the basic characteristics such as sex, age group, educational background, and marital status among all participants including withdrawal participants in the analysis.</p> </sec> <sec> <title>RESULTS</title> <p>Of the 5,111 initial survey respondents, 571 were regarded as fraudulent. The data of the remaining 4,540 participants (Male: 2273, Female:2267) included for analysis were well-balanced across participant gender and age group according to the sampling plan, because there was no significant difference by sex and age group using the chi-square test for checking the distribution bias of the participants (p=0.838). With compared to Female participants, male participants tended to be more likely to be managers and supervisors (Male:323, Female: 86), to work in a secondary industry (Male:742, Female: 357), and to have annual income ≥5 million yen (Male:976, Female:429). For the evaluation of a psychological indicator, Kessler 6 (K6), according to gender and age group, the characteristics of the score distribution of the included participants were similar to those reported in previous studies.</p> </sec> <sec> <title>CONCLUSIONS</title> <p>This study presents a protocol and an overview of the results of an Internet-based occupational health survey of workers. Using the results of this survey, we hope to evaluate the changes in occupational health activities and their impact on workers' health while controlling for the COVID-19 pandemic period.</p> </sec>