Aim The presence of cerebral white matter changes (WMC) has been reported as an important predictor of the rapidity of cognitive decline in Alzheimer's disease (AD). The association between the angiotensin‐converting enzyme (ACE) insertion/deletion (I/D) polymorphism and WMC in AD is yet to be elucidated. The present study aimed to examine the association between the ACE I/D polymorphism and WMC among AD patients in Taiwan. Methods A total of 403 patients clinically diagnosed with AD were recruited in a cross‐sectional study carried out in an area hospital in Kaohsiung, Taiwan. The ACE I/D polymorphism was genotyped, and cerebral white matter rating was carried out using the visual rating scale for age‐related white matter changes. Results The I allele was associated with a significantly lower total age‐related white matter changes scale score compared with the D allele (4.83 vs 5.93, P = 0.013). The total age‐related white matter changes scale score was significantly lower for the I/I genotype than for the I/D (4.37 vs 5.87, P = 0.009) and I/D + D/D genotypes (4.37 vs 5.91, P = 0.006), with no differences observed between the I/I + I/D and the D/D genotypes (5.08 vs 6.09, P = 0.373), after adjustment for age and hypertension. A stratified analysis by sex demonstrated that the I/I genotype was associated with significant lower WMC than other genotypes in women, but not in men. Conclusions The present study supports the hypothesis that the ACE I/D polymorphism is associated with the severity of WMC in patients with AD. Patients with AD who are homozygous for the I allele might be less likely to develop WMC, especially women. Geriatr Gerontol Int 2017; 17: 945–950.