At the start of 2020, a new coronavirus (COVID-19) invaded the world leading to the death of 3.92 million people. Sadly, to date, no remedy has been discovered for this virus. Preventive vaccines have been under investigation, but were unavailable until December 2020. Clinical deficiencies of nutrients may increase susceptibility to infections. This knowledge may have provided an incentive for some dietary supplement (DS) manufacturers to advertise their products as COVID-19 preventatives or cures without any substantiation, targeting mainly social media fans. The objective of this research was to assess the usage, knowledge and attitudes towards dietary supplementation before and during the COVID-19 pandemic among Lebanese people. A cross-sectional study was conducted based on a convenience sample (N = 2966) and information from participants aged 18 years and above was collected about periods before and during the pandemic. Our findings showed that attitudes towards DSs changed when the pandemic emerged and people believed that DSs can improve their health and strengthen their immunity. Despite the rise in DS prescription by healthcare professionals, the prevalence of DS use decreased from 73.3% before the pandemic to 69.9% during the pandemic (p < 0.001). Study results declared that the weekly or the daily estimated intake had increased during the pandemic as compared to before the pandemic, from 14% to 15.6% for antioxidants (p = 0.014), from 35.3% to 42.1% for vitamin C (p < 0.001), from 35.5% to 41% for vitamin D (p < 0.001), from 15.2% to 17.5% for vitamin E (p = 0.002), and from 18.8% to 29.3% for zinc (p < 0.001) and other vitamins and minerals (from 9% to 10.9%, p < 0.001). Binary logistic regression indicated that the use of DSs during the pandemic was 4 times higher among those infected with COVID-19, 30 times higher among those who used to take DSs before pandemic, and 1.5 times higher among those who worked in the medical sector. To conclude, there is a crucial need to increase awareness among Lebanese people regarding the use of DSs.