Soft electromechanical sensors have led to a new paradigm of electronic devices for novel motion-based wearable applications in our daily lives. However, the vast amount of random and unidentified signals generated by complex body motions has hindered precise recognition and practical applications of this technology. Recent advancements in artificial intelligence technology have made significant strides in extracting features from massive and intricate datasets, thereby presenting a breakthrough in utilizing wearable sensors for practical applications. Beyond traditional machine-learning techniques to classify simple gestures, advanced machine-learning algorithms have been developed to handle more complex and nuanced motion-based tasks with restricted training datasets. Thereby, machine-learning techniques have endowed the ability to perceive, and thus machine-learned wearable soft sensors have enabled accurate and rapid human gesture recognition, providing real-time feedback to users. This forms a crucial component of future wearable electronics, contributing to a robust human-machine interface. In this review, we provide a comprehensive summary covering materials, structures, and machine-learning algorithms for hand gesture recognition and possible practical applications through machine-learned wearable electromechanical sensors.