After the WHO declared COVID-19 a global pandemic, most countries resorted to declaring a period of lockdown to diminish the spread of the coronavirus. Lockdown and curfew were imposed in Saudi Arabia on March 23, 2020 for about three months. This study aimed to investigate the impact of COVID–19 lockdown on health-related determinants of eating behaviors and physical activity in Saudi Arabia using the Social Cognitive Theory (SCT). To gather information from the participants, semi-structured interviews with open-ended questions were used. A total of 41 interviews were conducted (20 males and 21 females). Most women expressed concern about gaining weight as a result of a rise in sweets and snacks, while fewer men expressed concern about weight due to lack of physical activity. The most popular foods purchased were fruits and vegetables aiming to improve health and boost immunity. Yet, increased snack and high-calorie food intake were the most frequently recorded. Most responses were marked by a high awareness about healthy eating. During the lockdown, physical activity declined, causing participants to become more stressed. Reliance increased on home-cooked meals and decreased on restaurants. The COVID-19 lockdown resulted in several changes in eating habits, including increased intake of snacks, sweets, fruits, vegetables, and home-cooked meals.