BackgroundPelvic organ prolapse (POP) is associated with cervical elongation (CE). The presence of CE could affect the surgical approach for the patient. Cervical length measurement using the pelvic organ prolapse quantification system (POP‐Q) has poor accuracy in CE detection. We speculated that transvaginal sonography of the cervix could be an alternative method to assess the cervical length properly.AimsWe aimed to compare cervical length based on POP‐Q examination with transvaginal sonography.MethodsThis was a prospective observational study of 99 patients with POP symptoms. POP‐Q staging was performed, and a gynaecologist determined cervical length. Moreover, all women underwent transvaginal sonography, and cervical length was reported. We used the inter‐class correlation coefficient and Bland–Altman plot to assess agreement. We used Spearman or Pearson correlation to determine the relationship between measurements difference and age, body mass index (BMI), total vaginal length, and parity.ResultsOne‐sample t‐test showed a significant difference between cervical length measured by POP‐Q and sonography (mean difference 9.93, 95% CI 8.26–11.93, p value <.001). The inter‐class correlation coefficient was reported as 0.476 (95% CI 0.22–0.65). The Bland–Altman plot illustrated considerable disagreement. There was no statistically significant correlation between measurement discrepancy and age, BMI, total vaginal length, or parity.ConclusionsThere is a significant discrepancy between the POP‐Q system and sonography in cervical length measurement. Given the importance of CE detection in choosing an appropriate surgical approach, it seems reasonable to repeat the measurement using alternative methods like sonography.