Background: An intra-abdominal abscess can sometimes become serious and difficult to treat. The current standard treatment strategy for intra-abdominal abscess is percutaneous imaging-guided drainage. However, in cases of subphrenic abscess, it is important to avoid passing the drainage route through the thoracic cavity, as this can lead to respiratory complications. The spread of intervention techniques involving endoscopic ultrasonography (EUS) has made it possible to perform drainage via the transmural route. Case presentation: We describe two cases of subphrenic abscess that occurred after intra-abdominal surgery. Both were treated successfully by EUS-guided transmural drainage (EUS-TD) without severe complications. Our experience of these cases and a review of the literature suggest that the drainage catheters should be placed both internally and externally together into the abscess cavity. In previous cases there were no adverse events except for one case of mediastinitis and pneumothorax resulting from transesophageal drainage. Therefore, we consider that the transesophageal route should be avoided if possible. Conclusions: Although further studies are necessary, our present two cases and a literature review suggest that EUS-TD is feasible and effective for subphrenic abscess, and not inferior to other treatments. We anticipate that this report will be of help to physicians when considering the drainage procedure for this condition. As there have been no comparative studies to date, a prospective study involving a large number of patients will be necessary to determine the therapeutic options for such cases.