Smartphones combine functionalities of many information and communication technologies and can eliminate the need of a separated utilization of phones, computers, cameras, and other digital devices. While most active and young people use smartphones, older adults predominantly stick to feature phones. The key two reasons for a low level of use of smartphones among older adults are related to the (perceived/anticipated) complexity of use and their low motivation which stem from psychophysical limitations of older adults. To cope with older adults’ specific needs, smartphone launchers have appeared on the market. They include an adapted user interface in order to make the use of a smartphone less complex. This master thesis aims to assess the usability of the Koala Phone Launcher and explores what are the most important issues experienced by older adults in this context. In the empirical part of the master thesis usability testing in combination with the think aloud method is employed to answer two research questions. The results showed that the adapted design of user interface of Koala Phone Launcher leads to better performance, efficiency and satisfaction among older adults. However, they also experience problems (when using advanced, mostly unsupported features of the tested launcher). In order to improve the user experience of older adults, a better integration of launcher's features and interface with a smartphone operating system would be needed.