Until now, the assessment of health care services provided by psychiatric institutions in Latvia has not been carried out and questionnaires to provide assessment from the patient’s perspective have not been adapted. For this study, a questionnaire that has been validated and successfully employed for several years in Norway was chosen to assess patients’ experience and in a psychiatric inpatient setting. The aim of the study was to determine patients’ satisfaction with the quality of mental health care services in Latvia in the subacute inpatient psychiatric ward in Rīga, adapting during this process the PIPEQ-OS (Psychiatric Inpatient Patient Experience Questionnaire) tool in Latvia. The pilot quantitative study was conducted from June 2016 till February 2017. In the study, an anonymous patient self-assessment questionnaire PIPEQ-OS containing 21 questions was used. During the adaptation process, the questionnaire was translated from English into Latvian and Russian and backwards. The quality and compliance of the translation was subsequently tested in cognitive interviews. During the study, 297 patients were discharged from the unit, and 231 of them completed the questionnaire. 12% of the completed questionnaires were not included in data processing due to being incorrectly filled in. Cognitive interviews with 20 patients were carried out; the average length of an interview was 15 minutes. Overall, the translation of the questionnaire proved to be relevant to the research theme. The subsequent factor analysis revealed three significant factors that reached the Cronbach’s alpha index of 0.7. Further studies using socio-demographic data and based on various inpatient units as well as the comparison of satisfaction indicators across different diagnostic groups are needed.