A French signal detection study identified an association between sulfonamide diuretics use, particularly furosemide, and lower Parkinson's disease (PD) risk. Our aim was to confirm this association in a Finnish nationwide nested case-control study (FINPARK), primarily in an indication-restricted case-control study of persons with heart or renal failure. Altogether 19 568 PD cases diagnosed in 1999-2015 and 130 156 age, sex and region-matched controls were included. The case-control study restricted to those with heart or renal failure included 1222 PD cases and 4766 matched controls. Furosemide use was identified from Prescription Register (1995-2015). The main analysis considered exposure at least 3 years before the matching date (3-year lag). Additional analyses with no lag, 5- and 8-year lags were conducted. Furosemide was not associated with PD risk (adjusted OR, 95% CI 1.00, 0.87-1.15 for user-non-user comparison with 3-year lag). A statistically significant borderline association between higher exposure levels and lower PD risk was observed in comparing risk across categories of cumulative furosemide exposure (adjusted OR, 95% CI 0.80, 0.64-1.00 with 3-year lag). Our nationwide indication-restricted case-control study of persons with PD found no robust evidence on the association between furosemide use and PD risk. However, there was suggestive evidence of reduced risk for participants in the highest exposure category.