PURPOSE: To establish if parathyroidectomy is beneficial for patient-reported outcomes (PROs), including quality of life (QoL), of patients with mild hypercalcemia ( < 1.0 mg/dl above the upper limit of reference ranges) caused by primary hyperparathyroidism without classic symptoms (mild PHPT). METHODS: We conducted a systematic review of the literature. Prospective studies were selected if PROs were measured before and after surgery and if the subpopulation of mild PHPT was clearly defined. Selected studies were appraised for their designs, PRO measures, and potential biases, as well as findings. Effect sizes were estimated to evaluate the extent of the benefits, if possible. RESULTS: Four randomized controlled trials and six observational studies were included in this analysis. Seven studies used the SF-36 to measure QoL and the other three used different scales. Quantitative data on outcomes were provided in the four observational studies, but effect sizes could not be estimated. A placebo effect of surgery was discussed in five studies. Statistically significant improvements in PROs were observed in all studies, but the clinical importance of the changes was not discussed in detail. CONCLUSIONS: The surgical treatment of mild PHPT may be associated with improved PROs, but the clinical significance of the changes is not yet confirmed.