Abstract Background Developing an imaging technique to map myelin changes in the brain within a short scan time is needed due to the inability of Alzheimer’s disease (AD) patients to remain motionless during MRI scanning. Purpose To investigate myelin loss in both AD and mild cognitive impairment (MCI) patients with a new myelin water mapping technique within reasonable scan time and evaluate the clinical relevance of the apparent myelin water fraction (MWF) values by assessing the relationship between decreases in myelin water and the degree of memory decline or aging. Method In this prospective study from March 2019 to October 2021, the participants were allocated as follows: 29 individuals were assigned to the cognitively normal (CN) elderly group (mean ± SD, 73 ± 5 years, 16 females), 32 participants were assigned to the MCI group (74 ± 5 years, 21 females), and 31 patients were assigned to the AD group (74 ± 6 years, 26 females). A 3D visualization of the short transverse relaxation time component (ViSTa)‐gradient and spin‐echo (GraSE) sequence was developed to map apparent MWF. Then, the MWF values were compared between the three participant groups, and was evaluated the relationship with the degree of memory loss. Result A total of 92 participants were evaluated. The AD group showed a reduced apparent MWF compared to the CN and MCI groups. Moreover, the MWF was decreased with age and positively correlated with Mini‐Mental State Examination scores. The largest AUC value (0.799) was in the corpus callosum and used to classify the CN and AD groups using the apparent MWF. Conclusion The ViSTa‐GraSE sequence can be a useful tool to map the MWF in a reasonable scan time. Combining the MWF in the corpus callosum with the detection of atrophy in the hippocampus can be valuable for group classification. Funding The research was supported by the National Research Foundation of Korea (NRF) grant funded by Ministry of Science and ICT (No. 2020R1A2C1004749, GHJ), Republic of Korea.