This book constitutes the proceedings of the 9th International Workshop on Sensor-Based Activity Recognition and Artificial Intelligence, iWOAR 2024, held in Potsdam, Germany, during September 26–27, 2024. The 15 full papers and 4 short papers presented here were carefully reviewed and selected from 28 submissions. These papers have been categorized into the following topical sections: Advances in Human Activity Recognition; Applications in Vision-Based Recognition; Wearable Devices and Health Monitoring; Novel AI and Machine Learning Approaches; Short Papers: Emerging Topics in Sensor-Based Systems.