Objectives The psychological effects of the COVID-19 pandemic may include anxiety. However, the association between demographic and physiological factors in COVID-19 associated anxiety symptoms is poorly understood. Therefore, the present cross-sectional study was conducted to examine anxiety symptoms and associated factors among patients with the SARS-CoV-2 omicron variant during quarantine in Shanghai. Methods The study was conducted between April 16, 2022, and May 21, 2022, at Fangcang Shelter Hospital in Shanghai, China. Data were collected using an anonymous online questionnaire. Demographic characteristics, respiratory symptoms, vaccine dose, comorbidities (such as hypertension and diabetes), type of work, and mental health symptoms were evaluated. Logistic regression was used to investigate the relationship between anxiety symptoms and risk factors. Stratification analysis was performed to investigate potential interactions. Results A total of 2132 patients with confirmed omicron variant SARS-CoV-2 infection were enrolled. The results showed that sex, age, type of work, respiratory symptoms, and comorbidities were positively associated with anxiety symptoms. Female gender (OR = 1.47, 95% CI = 1.11-1.94), nonmanual labor (OR = 1.62, 95% CI = 1.25-2.09), respiratory symptoms (OR = 3.19, 95% CI = 2.30-4.43), and other comorbidities (OR = 1.65, 95% = 1.09-2.50)were positively associated with anxiety symptoms. A significant interaction was observed between gender and nonmanual labor (OR = 1.54, 95% = 1.29-1.85), respiratory symptoms (OR = 2.06, 95% = 1.72-2.48), and comorbidities (OR = 1.57, 95% = 1.16-2.12), such that effects were stronger in women compared to men. There were also significant interactions between age group and nonmanual labor and respiratory symptoms in their association with anxiety symptoms. Conclusions Alleviation of respiratory symptoms, addressing comorbidities, and both psychological and psychopharmacological treatments may help reduce anxiety symptoms following infection with the SARS-CoV-2 omicron variant in mainland China.