High blood pressure (BP) increases the risk of cardiovascular disease, not only among middle-aged and older adults, but also in young adults. Early interventions for high BP may prevent future organ damage. Therefore, it is essential to monitor BP trends in young adults to support this approach. During the COVID-19 pandemic, a trend of increasing BP was observed worldwide. However, young adults have not been fully evaluated. Therefore, this study examined BP trends among university students (n = 106,691) over two decades, every 5 years from 2003 to 2023, including the period before and after the COVID-19 pandemic. From 2003 to 2018, there were no notable changes in BP. However, following the COVID-19 pandemic, increased BP was observed in both men and women, with systolic BP increasing from 118.1 (SD, 14.2) mmHg in 2018 to 120.6 (SD, 12.5) mmHg in 2023 among men, and from 104.6 (SD, 11.8) mmHg to 105.1 (SD, 11.7) mmHg among women. These trends were particularly pronounced among students with normal and underweight somatotypes and among first- and second-year students. The results of the lifestyle survey showed a decrease in smoking and drinking habits, insufficient sleep, mental stress, consumption of fast food and snacks, and an increase in exercise habits. Although contributing factors to the recent increase in BP were not identified, there was an upward trend in BP among Japanese university students. It is important to carefully observe how BP trends change over the long term following the end of the COVID-19 pandemic.