Despite strong support for the provision of memory assessment services (MASs) in England and other countries, their effectiveness in improving patient outcomes is uncertain. We aimed to describe change in patients’ health-related quality of life (HRQL) 6 months after referral to MASs and to examine associations with patient characteristics and use of postdiagnostic interventions. Data from 883 patients referred to 69 MASs and their informal caregivers (n=569) were collected at referral and 6 months later. Multivariable linear regression was used to examine associations of change in HRQL (DEMQOL, DEMQOL-Proxy) with patient characteristics (age, sex, ethnicity, socioeconomic deprivation, and comorbidity) and use of postdiagnostic interventions (antidementia medications and nonpharmacological therapies). Mean HRQL improved, irrespective of diagnosis: self-reported HRQL increased 3.4 points (95% CI, 2.7-4.1) and proxy-reported HRQL 1.3 points (95% CI, 0.5-2.1). HRQL change was not associated with any of the patient characteristics studied. Patients with dementia (54%) receiving antidementia drugs reported greater improvement in their HRQL but those using nonpharmacological therapies reported less improvement compared with those note receiving therapy. HRQL improved in the first 6 months after referral to MASs. Research is needed to determine longer term sustainability of the benefits and the cost-effectiveness of MASs.