The total duration of radiotherapy for patients with cervical cancer should be limited to 56 days to optimize treatment outcomes. This study aimed to statistically evaluate the effects of extended radiotherapy duration on survival and complications in 649 patients with cervical cancer treated with brachytherapy at our institution from 2014 to 2019. All patients had undergone intensity-modulated external beam radiation therapy, with 525 receiving two-dimensional (2D) brachytherapy and 124 receiving three-dimensional (3D) brachytherapy. Using the inverse probability of treatment weighting (IPTW) and propensity score matching (PSM), clinical data regarding treatment duration, survival outcomes, and complications were analyzed. PSM revealed that overall survival (OS) did not significantly differ between patients receiving prolonged treatment (>56 days) and those receiving treatment for a standard duration (<56 days) (P > 0.05). However, among patients who had received 2D brachytherapy, prolonged treatment correlated with increased recurrence and metastasis risks (P < 0.001); this trend was not evident in patients receiving 3D brachytherapy (P = 0.287). Higher FIGO stages were associated with worse OS and higher progression risks, which persisted post-IPTW adjustment. Extended radiotherapy duration was linked to a higher incidence of rectal and bladder reactions, particularly in the 2D group. Consequently, strictly controlling radiotherapy duration for patients receiving 2D brachytherapy is essential to reduce recurrence and metastasis risks. Close monitoring of rectal and bladder reactions is also recommended.