This book gathers peer-review contributions to the 4th International Workshop on Gerontechnology, IWoG 2021, held on November 23-24, 2021, in Évora, Portugal. They report on cutting-edge technologies and optimized workflows for promoting active aging and assisting elderly people at home, as well as in healthcare centers. They discuss the main challenges in the development, use and delivery of health care services and technologies.  Not only they propose solutions for improving in practice the monitoring and management of health parameters and age-related diseases, yet they also describe improved approaches for helping seniors in their daily tasks and facilitating their communication and integration with assistive technologies, thus improving their quality of life, as well as their social integration. All in all, this book provides health professionals, researchers, and service providers with extensive information on the latest trends in the development and practical application of gerontechnology, with a special emphasis on improving quality of life of the elderly.