<jats:sec><jats:title>Aim</jats:title><jats:p>The aim of this study was to investigate initial symptoms of early‐onset dementia (EOD) for each dementia subtype.</jats:p></jats:sec><jats:sec><jats:title>Method</jats:title><jats:p>We conducted a nationwide, population‐based EOD prevalence study in Japan. Data were collected through service providers for people with EOD. Initial symptoms were assessed in six domains: loss of memory, difficulty in word generation, irritability, loss of motivation, increased mistakes in the workplace or domestically, and unusual behaviours or attitudes other than those listed.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Participants were 770 people with EOD. Characteristic initial symptoms were observed for each EOD subtype. Loss of memory was more common in early‐onset Alzheimer's disease (75.7%, <jats:italic>P</jats:italic> < 0.001), difficulty in word generation was more common in early‐onset vascular dementia (41.3%, <jats:italic>P</jats:italic> < 0.001), and loss of motivation, increased mistakes in the workplace or domestically, and unusual behaviours or attitudes other than those listed were more common in early‐onset frontotemporal dementia (34.9%, <jats:italic>P</jats:italic> < 0.001; 49.4%, <jats:italic>P</jats:italic> < 0.001; 34.9%, <jats:italic>P</jats:italic> < 0.001, respectively). In addition, we observed gender differences whereby loss of memory was more common among women and irritability was more common among men. More than half of the participants were employed at symptom onset, and 57.2% of those who were employed at the onset had initial symptoms of increased mistakes in the workplace or domestically.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>This report reveals differences in the frequency of initial symptoms by EOD subtype. The results contribute to increasing public awareness of the initial symptoms of EOD, which will facilitate early diagnosis and social support.</jats:p></jats:sec>