OBJECTIVES: Our group has already demonstrated that patients' health-related quality of life (HRQL) improves in the first 6 months after their first appointment at memory assessment services (MASs), but the sustainability of such gains is unknown. We aimed to describe changes in patients' HRQL at 12 months after their first MAS appointment and to examine associations with patient and MAS characteristics. METHODS: We collected data from 702 patients and 452 lay caregivers at the first appointment and 12 months later. Multivariable linear regression was used to examine the relationships of change in HRQL (self-reported and proxy-reported) with patients' characteristics and use of post-diagnostic interventions, and multilevel models were used to analyse the relationships of HRQL with MAS characteristics. RESULTS: In the whole group, self-reported HRQL improved over 12 months (+3.5 points, 95% CI 2.7 to 4.2). Among people diagnosed with dementia, improvement in HRQL was more than double that among those with mild cognitive impairment or no diagnosis. Proxy-reported HRQL improved only in those diagnosed with dementia (+1.2 points, 95% CI 0.2 to 2.2). Changes in HRQL were not associated with any patient characteristics. The only feature of MASs associated with larger improvements in HRQL was the presence of advisory and support staff. CONCLUSIONS: Improvements in HRQL observed at 6 months are maintained up to 1 year after the first MAS appointment, more so among those who receive a diagnosis of dementia. Continued follow-up will determine if the improvement is even longer lasting.