Background <p>Endometriosis is one of the most common chronic diseases in women, with a prevalence of up to 10%. The disease particularly affects women of reproductive age. Endometriosis has a significant impact on the patient's quality of life (QoL). In the current study, we aimed to evaluate the role of early diagnosis of endometriosis on patients’ QoL.</p> Methods <p>In this longitudinal prospective study, 205 women with endometriosis who were referred to the gynecology department of Amir al-Mominin Hospital (Zabol-Iran) in 2021 were evaluated. Patients were divided into two groups based on the time of diagnosis, including early diagnosis and late diagnosis. An Endometriosis Health Profile (EHP) questionnaire was used to collect information about QoL before and 18&#xa0;months after treatment. Data were analyzed using SPSSv.26 software and significance level was considered less than 0.05.</p> Results <p>In both groups with early and late diagnosis, the QoL scores improved without significant difference (<i>p</i> = 0.303). There was a significant difference between lower stages (1 and 2) and higher stages (3 and 4) in terms of treatment effects on patients’ QoL, and higher stages of endometriosis affected patients’ QoL before and after treatment more than lower stages (<i>P</i> values &lt; 0.05).</p> Conclusion <p>Early or late diagnosis of endometriosis doesn’t affect patients’ QoL and patients benefit from treatment regardless of the time of diagnosis.</p>