Design guidelines and checklists are suggested as a useful tool in the development and evaluation of interface design of mobile phones for older adults. Given the intense evolution of mobile phone design, understanding how the design guidelines and checklists have taken into account the advances in mobile phone usability for older adults is important for their correct application and future development. Thus, this study explores the usability dimensions of mobile phone design for older adults and the related changes in terms of time and the type of device (feature phones vs. smartphones) based on an expert coding of the eight mobile phone design guidelines and checklists for older adults published between 2006 and 2014. The results of the expert coding show that design guidelines and checklists most frequently deal with visual and haptic issues (e.g., high contrast, button type, and button size), whilst they hardly ever address various elements of textual interface (e.g., ease of text entry, a button’s feedback, and font type). Over time, the design guidelines and checklists have become more complex in terms of the average number of included usability categories and dimensions. For smartphones, the guidelines, on average, put more emphasis on the screen, touchscreen, text, and exterior related issues, whereas the design guidelines for feature phones stress the usability of the keypad and menus. Besides revealing potential usability dimensions that could be further expanded in the guidelines, this study also highlights the need for research that would empirically validate the design guidelines and checklists in the future.