Complications of hemodialysis (HD) treatment include hypotension, hypertension, imbalance syndrome, and chest pain. The incidence of hypotension ranges from 25 to 50%, making it as the most common complication during HD. Repeated hypotension causes blood stagnation and leads to excessive heart workload of patients. Moreover, clinical studies proposed that the incidence of hypotension has a high correlation with the rate of mortality. In clinical practice, blood pressure (BP) measurement by nursing staff every 30 to 60 min or the patient claiming of discomfort is required to detect intradialytic hypotension (IDH). In this study, we developed an evaluation system using photoplethysmography (PPG) sensors for IDH monitoring. The system acquired heart rate variability (HRV) from PPG sensors and arterial pressure (AP) from dialysis machines to provide an immediate classification of IDH risk. We divided IDH patients into three classes from low to high risk, with the third category having the highest risk. To verify the accuracy of the system, we designed a clinical trial to compare measurements obtained with the system with BP measurements taken by clinical staff. The results from 12 patients indicated that the accuracy of the proposed system was 90%, indicating its high potential to provide a simple and fast assistance system for assisting in the clinical evaluation of IDH.