Fan support is a critical component of home advantage across many sports. Whether the impact is on referee decision-making or psychologically affecting opposing teams, fans influence the outcome of games. Due to the COVID-19 pandemic, the 2020–2021 college basketball season created the opportunity to explore home advantage when few or no fans were allowed to attend games. We exploit large differences in season attendance to measure the impact of fans on home advantage in the season before the pandemic and in an attendance-restricted season during the pandemic. Our results find that a decrease in attendance reduced home advantage. Furthermore, policies restricting attendance during the COVID-19 pandemic more strongly impacted the home advantage in games played by two teams in power conferences relative to games played between two teams in non-power conferences.