This paper adopts a longitudinal approach toward examining what lies behind income mobility of older people aged 50 and over in England and aged 45 and over in South Korea over the period between 2006 and 2012, using panel data from the English Longitudinal Study of Ageing (ELSA) and the Korean Longitudinal Study of Ageing (KLoSA). The breakdown of income mobility which takes into account different type of division of the elderly population and income sources are also performed. The findings reveal that income growth has very little impact on aggregate income mobility in England, while it is crucial for the income mobility levels in Korea. There is a great deal of income mobility among single people under the age of 65 in England, while older people who are aged 65 or above and live alone experienced a greater variation in their income over time in Korea. In the case of breakdown of income mobility by income sources, it appears that labor income is the most important determinant of mobility in both countries and income from self‐employment for Korea and income from social transfers in England also plays an important contribution to income mobility.