Informal caregivers of persons with dementia often report high levels of anxiety, depression and burden. Nonetheless, other less evaluated psychological symptoms might also influence their health-related quality of life (HRQoL). The aim of this study was to comprehensively analyse other psychological symptoms and their influence on the health-related quality of life of informal caregivers. Fifty-four informal women caregivers and fifty-six women non-caregivers were recruited to participate in the study. Psychological symptoms were assessed using the Symptom Check-List-90-Revised (SCL-90-R) questionnaire and the HRQoL with the EuroQoL-Five Dimensions and Three Levels (EurQoL-5D-3L) questionnaire. Significant between-group differences were found in the majority of scales in the SCL-90-R questionnaire (p < 0.01) and caregivers also reported a worse HRQoL than non-caregivers (p < 0.05). Several psychological symptoms such as obsession-compulsive (beta = 0.47), hostility (beta = 0.59), and somatization (beta = 0.49) had a significant impact on caregivers' HRQoL (R-2 explained between 0.17 and 0.30 of the variance). Caregivers are at a higher risk of suffering other psychological symptoms and show a moderate-high level of psychiatric morbidity, which therefore explains the poorer HRQoL outcomes. Supporting interventions should be provided to mitigate these psychological symptoms in order to improve their general distress and HRQoL.