<p>We aimed to evaluate the successful long-term use of dienogest for the management of pelvic pain and bleeding control in perimenopausal women with symptomatic adenomyosis using real-world data. All women aged ≥ 40 years with adenomyosis who complained of dysmenorrhea and/or menorrhagia and received dienogest between September 2018 and December 2021 were retrospectively recruited. The primary outcome was successful long-term use of dienogest for pelvic pain and/or bleeding control. A total of 87 women were analyzed. Overall, forty-nine (56%) patients had excellent pain control, but 17 (20%) eventually underwent hysterectomy, while 21 (24%) received dienogest for over 24 months (mean 33.5 ± 8.5 months). According to subgroup analysis by age (≥ 45 vs. &lt;45), older women easily discontinued dienogest due to side effects (51% vs. 30%, <i>p</i> = 0.047) but less frequently changed to surgery (11% vs. 30%, <i>p</i> = 0.012) than younger women. Older age, higher CA-125 value, and larger uterine size before treatment were linked to poorer long-term responses to dienogest. As risk factor, uterine volume &gt; 352.7 cm³ reflects easier treatment failure (sensitivity = 65.4%, specificity = 66.7%, area = 0.68, <i>p</i> = 0.032). In perimenopausal women with symptomatic adenomyosis, nearly half of the treated patients benefitted from dienogest. Our informative findings can assist clinicians in pre-treatment counseling and identifying factors correlated with treatment effectiveness.</p>