A posture and breathing improvement device, system, and method. The system for improving posture and deep breathing may comprise: a sensor device; posture/breathing improvement software program, comprising one, both, or a combination of a posture improvement system interface and a breathing improvement system interface; and one or more user devices. The sensor device may be physically associated with a user and may communicate with the posture improvement software program. The sensor device may comprise: one or more sensors for monitoring positions and movements of the user. The system may calculate one or more optimum postural positions and breathing exercises for the user, based on data communicated by the sensor device and collected information about the user. The system may monitor a conformance of the user with the optimum postural positions and may display the conformance on the posture improvement system interface. The system may detect and notify the user of one or more non-conformances, such that a user is reminded to maintain at least one optimum postural position and periodically take deep breaths.