The objective of this study was to determine whether an asynchronous smartphone-based application with image-based questions would improve anesthesiology resident transesophageal echocardiography (TEE) knowledge compared with standard intraoperative teaching alone.Prospective, single-blinded, pilot, randomized controlled trial.Large university teaching hospital.Participants were anesthesiology residents on their cardiac anesthesiology rotation.EchoEducator, a TEE image-based smartphone application of learning content through questions, was developed. Content was derived from the Examination of Special Competence in Basic Perioperative Transesophageal Echocardiography and the Objective Structured Clinical Examination portion of the APPLIED Examination and focused on identification of basic TEE views, cardiac structures, and pathology. Residents were randomly assigned to receive access to either the application or to standard intraoperative teaching. Thirty residents met inclusion criteria, and 18 residents completed the study. A pre-intervention assessment was given at the beginning of the rotation, and a post-intervention assessment was given after 2 weeks.The primary outcome was the difference between the post-test score and the pre-test score. Standard bivariate statistics and the chi-square test were used for categorical variables, and the Student t test was used for continuous variables. Tests were 2-sided, and statistical significance was set at p < 0.05. The intervention group demonstrated a greater increase in score; (+19.19% [95% confidence interval 4.14%-34.24%]; p = 0.02) compared with the control group.This study supports the hypothesis that use of a smartphone-based asynchronous educational application improves TEE knowledge compared with traditional modalities alone. This supports an opportunity to improve medical education by expanding the role of web-based asynchronous learning.