Addressing the problem of disabilities and disability deterioration is a key task for healthy ageing. Financial aid has been an effective measure for vulnerable groups, especially ageing people with disabilities. However, the effects of targeted financial aid on preventing disability deterioration remain unknown. The Chinese government launched a targeted financial aid programme aimed at people with disabilities. In this study, we investigated the causal effects of such targeted financial aid on disability deterioration prevention for elderly people with disabilities in China. The data set used in this study included 36 640 elderly individuals with disabilities in China between 2016-19. We constructed a quasi-experiment approach and used a difference-in-differences (DID) method to examine the counterfactual differences between the treatment group in four cities that implemented such targeted financial aid in 2018 and the control group in three cities that did not adopt the policy over the study period. We employed propensity score matching (PSM) jointly with DID to mitigate selective bias. For sensitivity analysis, we conducted supplementary analyses on alternative samples, focusing on each of the treated cities respectively. Besides the main outcome, we also used fixed effect models to test the impact of such financial aid on rehabilitation access. The targeted financial aid significantly reduced the possibility of disability deterioration for elderly people with severe disabilities (0.26%; P < 0.001). Using PSM-DID models, the impact remained significant (0.33%; P < 0.001). Moreover, financial aid was significantly related to their access to rehabilitation services (12.71%; P < 0.001). Further analysis showed the heterogenous effects of targeted financial aid across individual demographic and socioeconomic factors, as well as communities with and without rehabilitation facilities. Targeted financial aid had a positive impact on preventing disability deterioration among elderly individuals aged ≥65 years with severe disabilities. Moreover, rehabilitation care had a potential mediating role in the relationship between targeted financial aid and disability deterioration prevention. This study highlights the effectiveness of targeted financial aid in preventing disability deterioration and improving rehabilitation care for people with disabilities.