To evaluate the factors associated with the laterality of recurrent endometrioma after conservative surgery. The laterality of primary endometrioma and characteristics of patients were evaluated according to the laterality of recurrent endometrioma in 140 participants who underwent second procedures after conservative surgical treatment. From 2000 to 2011, 2,214 patients underwent primary conservative surgery for endometrioma at our institution. Endometriomas were located on the left in 866 patients (39.1%), the right in 772 (34.9%) and bilaterally in 576 (26.0%). Histologically confirmed recurrent endometriomas were found in 140 patients: on the left in 49 patients (35.0%), on the right in 44 (31.4%) and bilaterally in 47 (33.6%). The sites of primary endometrioma were not associated with those of recurrent endometrioma, and the recurrence rate in the treated ovary (59.8%) was similar to that of the intact ovary (69.0%) at the primary surgery. Proportions of stage IV endometriosis and posterior cul-de-sac obliteration were higher in patients with bilateral recurrence than in those with unilateral recurrence (p<0.01 for all comparisons) and in patients with contralateral recurrence than those with ipsilateral recurrence (p<0.05 for all comparisons), but no differences were found in other characteristics of participants according to the laterality or pattern of recurrence. The lateral distribution of recurrent endometrioma was not associated with that of the primary lesion, and endometrioma did not recur more frequently in the treated ovary. An advanced stage and the presence of posterior cul-de-sac obliteration were factors associated with bilateral or contralateral recurrence of endometrioma.