Introduction The COVID-19 pandemic has been affecting the lives of millions of people globally. Patients recovering from COVID-19 are facing, not only the symptom of long COVID, but also psychological problems, such as sleep disturbance. This study aims to assess the proportion of COVID-19 recovered adult patients that suffer from insomnia and associated factors in Vietnam. Methods A cross-sectional study was performed between January and March 2022 among patients who have recovered from a COVID-19 infection. Data were collected based on a self-administered questionnaire that included sociodemographic and standardized questionnaires from the Hospital Anxiety and Depression Scale (HADS), the Perceived stress scale (PSS) and the dependent variable using Insomnia Severity Index (ISI). Multivariable logistic regression was conducted to explore factors associated with the patients’ insomnia disorder. Results A total of 325 participants were included in this analysis, 34.5% of participants had insomnia. According to multivariable logistic regression, participants who were equal to and over 50 years of age, feeling alienated from others, and were not supported by families or relatives, reported significantly higher levels of insomnia disorders over those aged under 50 years, having closer ties with family and had received support from family or relatives. Besides, respondents who recorded mental health problems that included anxiety, depression and stress were more likely to get insomnia disorders than those without mental health symptoms (OR 2.7, 95% CI 1.1–6.6) (OR 4.5, 95% CI 2.3–8.9) (OR 2.3, 95% CI 1.1–5.3), respectively, all p < 0.05. Conclusion There was a remarkable rate of COVID-19 recovered patients experiencing insomnia disorders. Older age, alienated relationships and not being supported by families or relatives, as well as had mental health problems, are factors that affected the patients’ insomnia, which showed that these sleep issues need to be screened and managed among adults who have recovered from COVID-19.