'Shelter in place' and 'lockdown' orders implemented to minimize the spread of COVID-19 have reduced opportunities to be physically active. For many, the home environment emerged as the only viable option to participate in physical activity. Previous research suggests that availability of exercise equipment functions as a determinant of home-based physical activity participation among the general adult population. The purpose of this study was to use a socioecological framework to investigate how the availability of exercise equipment at home predicts behavioral decisions, namely, intention, planning, and habits with respect to participation in physical activity. Participants (n = 429) were adults recruited in U.S. states subject to lockdown orders during the pandemic who completed measures online. A structural equation model indicated that availability of cardiovascular and strength training equipment predicted physical activity planning. Social cognition constructs mediated the relationship between each type of exercise equipment and intentions. Autonomous motivation and perceived behavioral control were found to mediate the relationship between each type of exercise equipment and habit. The availability of large cardiovascular and strength training equipment demonstrated significant predictive effects with intention, planning, habit, and autonomous motivation. Facilitating these constructs for home-based physical activity interventions could be efficacious for promoting physical activity.