Abstract To explore the interaction of instrumental activities of daily living (IADLs) and dual sensory function on cognition in the elderly. A cross‐sectional survey was conducted in six general hospitals in China, from October 2022 to December 2022. Data collection included general information, IADLs scale, self‐reported sensory function questionnaire, and mini‐mental state examination (MMSE). Binary logistic regression was used to examine the association between factors and cognition. The interactive effect was evaluated by synergy index (S), relative excess risk due to interaction (RERI), and attributable proportion due to interaction (AP). The odds ratio (OR) of IADLs decline in cognition is 4.412 (95% confidence interval [CI]: 3.633–5.358, p