The aim of this study was to explain possible relationships in cases of ectopic pregnancy between sonographic endometrial features and treatment outcome following methotrexate (MTX) injection. A total of 157 cases of unruptured tubal pregnancy were diagnosed and treated systemically with MTX. The sonographic endometrial pattern, endometrial thickness and treatment outcome were retrospectively analyzed. There were four types of endometrial patterns: these were trilaminar, homogeneous, heterogeneous and pseudosac. Success rates following MTX treatment were different for each group: these were 64.7%, 78.4%, 50.0% and 46.2%, respectively (p = 0.0129). And the risk of treatment failure was increased 3.64 times (95% CI 1.56 to 8.49) in heterogeneous thick pattern and 4.24 times (95% CI 1.18 to 15.23) in pseudosac pattern. In conclusion, when tubal pregnancy was seen in a pseudogestational sac pattern or a heterogeneous pattern, the failure rate of medical treatment was increased. This can serve as a reference for considering the decision about medical treatment in women with unruptured tubal pregnancy.