Due to inadequate human and financial resource support, the development of mental health services in Cambodia has been undertaken by various non-governmental organizations (NGOs). Schizophrenia is the most common functional psychotic disorder, causing severe and chronic symptoms, and the programs provided by the NGOs should have enhanced the quality of life (QoL) of patients and their caregivers; however, epidemiological research, which is a driving force behind the recognition of mental health as a global public health concern, is lacking for schizophrenia in Cambodia. This study therefore aimed to create QoL evaluation questionnaires available in Khmer (the Cambodian language) for patients with schizophrenia and family caregivers, and to identify the social determinants and predictors of their QoL. This cross-sectional study recruited 59 patients and 59 caregivers attending three clinics operated by two NGOs: the Transcultural Psychosocial Organization (TPO) Cambodia and the Supporters for Mental Health (SUMH) Cambodia. We conducted linguistic validation of the Schizophrenia Quality of Life Questionnaire 18-item version (S-QoL 18) and the Schizophrenia Caregiver Questionnaire (SCQ), then analyzed correlations between the QoL dimensions and socio-demographic factors. The main findings of this study were as follows: 1) the newly created Khmer versions of S-QoL 18 and SCQ are relatively good psychometric tools that are suitable for research to identify patients’ and caregivers’ needs to improve their QoL; and 2) engaging in paid work or being of the post-Khmer Rouge generation results in higher QoL for patients, but having low household economic status or being affected by chronic disease leads to lower QoL for family caregivers. These findings are useful for enabling community mental health professionals and aid organizations to create programs to lessen the patient and caregiver burden in Cambodia. Further research is necessary to develop practical projects that will improve patients’ and caregivers’ QoL in various clinical settings in Cambodia.