Objective: This study aimed to translate the IIEF-5 questionnaire into Indonesian and perform a validity and reliability assessment of the translated instrument. Material and Methods: A methodological study on 106 male outpatients, recruited consecutively, was carried out in a tertiary hospital in Surabaya, East Java from January to March 2020. This study was conducted in two stages: translation and validation. Two independent sworn translators performed a forward and backward translation of the first draft. The final version was synthesized by a team of experts comprised two urologists and another sworn translator. The validity of the questionnaire is determined through a Pearson correlation analysis. Cronbach’s a internal consistency measurement was used to assess its reliability. Interrater reliability between the patient and the physician was measured using the Cohen’s j coefficient. Results: Pearson’s “r” value is significantly higher than the critical value table and indicates a high to a very high level of validity based on Guilford’s interpretation (r ¼ 0.70-1.00). A good internal consistency is shown by the Cronbach’s a coefficient value (a ¼ 0.828). An almost perfect agreement between the patient’s results and the assessment made by the physicians is shown by the Cohen’s j coefficient value (j ¼ 0.879, P < .001). Conclusion: The Indonesian IIEF-5 is a valid and reliable patient-reported outcome measure for evaluating erectile dysfunction in the literate middle-aged and older adult male population in Indonesia.