Background: Poland is one of Europe’s most religious societies. Methods: The article presents the results of an online survey conducted in April 2020 during the period of the Polish government’s strictest restrictions to date in response to the pandemic. A quota sample of 1001 adult Poles was surveyed. Results: Around one-fifth (21.3%) of people declared that they spent more time praying and engaging in other religious practices than previously. As many as 61.3% of people who previously practiced religion several times a week spent more time on these practices, and, more interestingly, religious observance also increased among people who had previously practiced only once every few years (15.9%) and those who had not previously practiced at all (7.4%). People who previously practiced sporadically or not at all, but who began to pray more during the pandemic, are found to be distinguished from others by a greater fear of losing their job. Spending more time on religious observance is shown to be related to, e.g., disregard for some government restrictions, possession of less knowledge about COVID-19, and a greater tendency to believe in conspiracy theories. Conclusions: Overall, religious practices increased during the Polish spring lockdown. Although these increases are unlikely to be long-lasting, changes in religiosity caused by COVID-19 appear to be a real phenomenon. As the pandemic continues, more research on different aspects of this phenomenon is needed.