Objective Little is known about the trajectory of health and well‐being from before to after a cancer diagnosis. This study aimed to examine changes in health and well‐being across three time points (0–2 years before a cancer diagnosis, 0–2 years post‐diagnosis and 2–4 years post‐diagnosis) in individuals receiving a new cancer diagnosis, and at matched time points in a cancer‐free comparison group. Methods Data were from waves 1–6 of the English Longitudinal Study of Ageing. Repeated‐measures ANOVAs were used to examine differences in self‐rated health, mobility impairments, activities of daily living impairments, quality of life, depressive symptoms and life satisfaction by group and time, and group‐by‐time interactions. Results Of the 4565 participants with data from three time points, 444 (9.7%) reported a new cancer diagnosis. Those in the cancer group reported poorer self‐rated health (p < .001), quality of life (p < .001) and life satisfaction (p < .01) than participants in the comparison group, and a higher proportion reported depressive symptoms (p < .001) and impairments in mobility (p < .001) and activities of daily living (p < .001). All markers of health and well‐being worsened significantly over time. The group‐by‐time interaction was significant for self‐rated health (p < .001), with a greater decline in health over time in the cancer group. Conclusions Cancer survivors in this sample had poorer health and well‐being than those with no diagnosis, and self‐rated health deteriorated more rapidly following a cancer diagnosis. Screening for these factors around the time of a cancer diagnosis could allow for interventions to be targeted effectively and improve the health and well‐being of cancer survivors. © 2015 The Authors. Psycho‐Oncology published by John Wiley & Sons Ltd.