Purpose <p>To compare the effects of the gonadotrophin-releasing hormone (GnRH) agonist protocol, GnRH antagonist protocol, progestin-primed ovarian stimulation (PPOS) protocol, and mild stimulation/natural cycle protocol on the cumulative live birth rate (CLBR) in patients with adenomyosis and Poseidon group 3/4.</p> Methods <p>A total of 1090 patients diagnosed with adenomyosis and Poseidon groups 3/4 group who underwent in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) from January 2013 to December 2020 were included. Demographic characteristics, laboratory indicators, and clinical outcomes of the four ovarian stimulation protocols were compared. The primary outcome was the CLBR, with binary logistic regression analysis used to explore the factors influencing CLBR.</p> Results <p>Among the patients with adenomyosis and Poseidon groups 3/4, the CLBR in GnRH agonist protocol group was higher than that in PPOS protocol group (45.78% vs. 22.33%, <i>P</i> = 0.005). Binary logistic regression analysis revealed that GnRH agonist protocol had a higher CLBR compared to PPOS protocol (adjusted odds ratio (aOR) 3.26, 95% confidence interval (CI): 1.56–6.83, <i>P</i> = 0.002), while no significant differences were found when comparing PPOS protocol with GnRH antagonist protocol (<i>P</i> = 0.093) and mild stimulation/natural cycle protocol <i>(P</i> = 0.125). In the &lt; 35&#xa0;years subgroup, the CLBR of GnRH agonist protocol was significantly higher (55.26% vs. 33.82%; <i>P</i> = 0.032), which wasn’t observed in elder subgroups (<i>P</i> &gt; 0.05).</p> Conclusion <p>For patients with both adenomyosis and Poseidon groups 3/4, GnRH agonist protocol showed a higher CLBR, especially in patients &lt; 35&#xa0;years (Poseidon group 3).</p>