Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to spread globally, causing unprecedented effects on global health and economies. Community-based serological data are essential for understanding the true prevalence of infections, specifically the subclinical infections, as COVID-19 asymptomatic infections are common. Such data would also be important for decision making around choosing appropriate epidemiological control measures, as well as for the true estimation of mortality rates in the population. Further, determining the seroprevalence of anti-SARS-CoV-2 antibodies in the population would provide important information on herd immunity. In this study, we conducted a population-based age-stratified serological study to understand the prevalence of SARS-CoV-2 in Jazan Province, Saudi Arabia. Out of 594 participants who were recruited from 29 August to 30 December 2020, just before the vaccination rollout program in Saudi Arabia, about 157 were seropositive for SARS-CoV-2, indicating an estimated seropositivity rate of 26%. Although no significant difference in seropositivity was seen between male and female participants, we found that lower seroprevalence was associated with the younger (below 18 years old) and older populations (older than 56 years) compared with other age groups (19–55 years). These data indicate a high prevalence of SARS-CoV-2 antibodies following the peak of COVID-19 spread in Jazan province; however, most of the population (three-quarters) remains susceptible to SARS-CoV-2 infection.