Individuals with a mental disorder experience substantial health disparity and are less likely to participate in cervical screening and human papillomavirus vaccination. Additionally, this population may benefit less from tertiary cancer prevention. To compare clinical characteristics and survival patterns between patients with cervical cancer with and without a preexisting diagnosis of a mental disorder at the time of cervical cancer diagnosis. This cohort study obtained data from Swedish population-based (Swedish Cancer Register, Swedish Cause of Death Register, Swedish Total Population Register, Swedish Patient Register, and Swedish Longitudinal Integration Database for Health Insurance and Labor Market Studies) and quality registries (Swedish Quality Register of Gynecologic Cancer and Swedish National Cervical Screening Register) on patients with cervical cancer. Patients who were included in the analysis were identified using the Swedish Cancer Register and were diagnosed with cervical cancer between 1978 and 2018. The Swedish Patient Register was used to identify patients with mental disorders using codes from the International Classification of Diseases, Eighth Revision and Ninth Revision and the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision. Because data on clinical characteristics at the time of cancer diagnosis were available for only for part of the study population, 2 patient groups were created: those with cervical cancer diagnosed from 2002 to 2016 and all patients diagnosed with cervical cancer (1978-2018). Data analyses were carried out between March and September 2022. Clinical diagnoses of a mental disorder, including substance abuse, psychotic disorders, depression, anxiety, stress-related disorders, attention-deficit/hyperactivity disorder, autism, and intellectual disability, prior to cervical cancer. Death due to any cause or due to cervical cancer as ascertained from the Swedish Cause of Death Register. The sample included 20 177 females (mean [SD] age, 53.4 [17.7] years) diagnosed with cervical cancer from 1978 to 2018. In a subgroup of 6725 females (mean [SD] age, 52.2 [18.0] years) with cervical cancer diagnosed from 2002 to 2016, 893 (13.3%) had a preexisting diagnosis of a mental disorder. Compared with patients with no preexisting mental disorder diagnosis, those with a preexisting mental disorder had a higher risk of death due to any cause (hazard ratio [HR], 1.32; 95% CI, 1.17-1.48) and due to cervical cancer (HR, 1.23; 95% CI, 1.07-1.42). These risks were lower after adjustment for cancer characteristics at the time of cancer diagnosis (death due to any cause: HR, 1.19 [95% CI, 1.06-1.34] and death due to cervical cancer: HR, 1.12 [95% CI, 0.97-1.30]). Risk of death was higher for patients with substance abuse, psychotic disorders, or mental disorders requiring inpatient care. Among patients with cervical cancer diagnosed from 1978 to 2018, the estimated 5-year survival improved continuously during the study period regardless of preexisting diagnosis of a mental disorder status. For example, in 2018, the estimated 5-year overall survival proportion was 0.66 (95% CI, 0.60-0.71) and 0.74 (95% CI, 0.72-0.76) for patients with and without a preexisting diagnosis of a mental disorder, respectively. Findings of this cohort study suggest that patients with cervical cancer and a preexisting diagnosis of a mental disorder have worse overall and cervical cancer-specific survival than patients without a preexisting mental disorder diagnosis, which may be partly attributable to cancer and sociodemographic characteristics at diagnosis. Hence, individuals with mental disorders deserve special attention in the tertiary prevention of cervical cancer.