AimTo clarify the effects of small endometriomas on in vitro fertilization (IVF) outcomes. In the present study, the potential impact of small ovarian endometriomas on the quantitative and qualitative outcomes of IVF was evaluated in the same individual.MethodsA retrospective analysis was performed, in which 118 infertile women with unilateral endometriomas that were <40 mm in size and who underwent IVF or intracytoplasmic sperm injection were evaluated. Single frozen embryo transfer cycles were performed, with separate data collections for both the affected and the unaffected ovaries, which allowed for an evaluation of the implantation rate.ResultsThe mean antral follicular count and the number of follicular flushings, retrieved oocytes, and obtained embryos were significantly lower for the endometrioma‐containing ovary than for the contralateral, intact ovary. No significant difference was observed regarding the blastocyst retrieval and good‐quality blastocyst retrieval rates, pregnancy rate, and clinical pregnancy or live birth rate.ConclusionAlthough the patients with a small endometrioma had a decreased ovarian reserve, they had lower pregnancy rates. The decision to transfer an embryo from an endometrioma‐containing ovary or from a contralateral, intact ovary also might not influence the pregnancy rate.