Background Many international studies have reported the outcomes and predictors of coronavirus disease 2019 (COVID-19); however, only a few national studies have reported predictors of poor outcomes among adult hospitalized patients with COVID-19. Therefore, this study aimed to describe the clinical characteristics and complications of COVID-19 and identify predictors of poor outcomes. Methods This was a retrospective cohort study. All adult patients confirmed with COVID-19 who were admitted at the King Abdulaziz Medical City (KAMC)-Jeddah between March 1, 2020, and December 31, 2020, were included; pediatric and pregnant patients were excluded. The clinical features and complications of COVID-19 were tested for association with poor outcomes (intensive care unit [ICU] admission or death) using chi-square and Fisher’s exact tests. In addition, logistic regression analysis was performed to identify the predictors of poor outcomes. Results A total of 527 patients were included in this study. Forty-two patients (8%) (6-10, 95% confidence interval [CI]) died: 13 in the general wards and 29 in the ICU. Of the 84 patients admitted to the ICU, 65 underwent invasive mechanical ventilation. Poor outcome affected 97 patients (18%) (15-22, 95% CI). Shortness of breath, oxygen saturation <92%, and abnormal chest x-ray findings were associated with poor outcomes (P-value < 0.001). In addition, lymphocyte counts were significantly lower, while c-reactive protein levels were significantly higher among patients with poor outcomes (P-value < 0.001). The most common complications were acute cardiac (83 patients, 16%), acute kidney (78 patients, 15%), and liver injuries (76 patients, 14%). Predictors of poor outcome were the updated Charlson comorbidity index (CCI) (odds ratio [OR] 1.2 [95% CI 1.1-1.4]), liver injury (OR 2.6 [95% CI 1.3-4.9]), acute kidney injury (OR 4.3 [95% CI 2.3-7.8]), and acute cardiac injury (OR 5.1 [95% CI 2.8-9.4]). Conclusions COVID-19 disease is associated with significant morbidity and mortality. Predictors of poor outcomes among COVID-19 hospitalized patients were the updated CCI, liver injury, acute kidney, and acute myocardial injuries. Subsequently, the risk of poor COVID-19 outcomes is increased among patients with multiple comorbidities and/or multiple COVID-19 complications.