The COVID-19 pandemic and related restrictions have significantly impacted the quality of life of society in many countries in various aspects. The purpose of this study was to examine how the COVID-19 pandemic affected the consumption of meat and fish in society in Poland as well as the factors that determined these changes. The cross-sectional study was conducted using an original online questionnaire between 8th and 18th of April 2020. The subjects were selected randomly. The target population were adults living in Poland. The inclusion criterion for the study was the age of at least 18 years and consent to selfless participation in the study. Communication via social media such as Facebook or Instagram was used to enroll more participants from different socio-demographic subgroups. The questionnaire was divided into two parts—the first part contained questions about sex, age, body mass, body height, residence, level of education, and occupation, and the second part consisted of specific questions about the consumption frequency of different kinds of meat during the COVID-19 lockdown period (in comparison to the time before the pandemic). A total of 3888 people took part in the study including 84.54% women, with an average age of 30.17 ± 9.22 years. The frequency of poultry consumption increased, while for pork, beef, ham and other meat products as well as fish and seafood it declined. The factors that influenced the change in dietary patterns during the lockdown related to the COVID-19 pandemic included age, body mass index, gender, place of residence, and type of work performed. However, no relationship was found between the change in meat and fish consumption during the pandemic and the level of education and form of employment during the pandemic.