Aim The financial interests of care management agencies can affect how care managers assist clients' use of long‐term care insurance services. The present study examined the relationship between clients' service expenditures, and whether the home help and day care service agencies belonged to the same organization as the care management agency. Methods Population‐based data were obtained from a suburban municipality in Japan. We investigated 4331 persons with care needs certificates (levels 1–5), including those using home help (n = 1780) or day care (n = 2141) services. Data on the service expenditures, and clients' and agencies' characteristics were analyzed using multiple linear regression analyses controlling for potential confounders. Results Home help service users spent an average of US$558.1 ± 590.1 for home help service, and day care service users spent US$665.0 ± 415.9 for day care service. Living alone, living in a condominium/apartment, higher care needs, more severe cognitive impairment and lower use of other services were associated with higher home help service expenditure. Day care service expenditure increased with older age, female sex, higher care needs, more severe cognitive impairment and higher physical function. Clients whose service agencies and care management agencies belonged to the same organization had higher expenditures, even after adjusting for confounders (home help: β = 0.126, P = 0.007; day care: β = 0.085, P = 0.002, respectively). Conclusions Financial interests of care management agencies might significantly influence clients' service expenditure. We should develop an effective system to minimize this influence. Geriatr Gerontol Int 2017; ••: ••–••.