The incidence and 5-year recurrence rate of urothelial carcinomas (UCs), including UC of the bladder (UCB) and upper urinary tract UC (UTUC), have increased annually. There is a great need for a simple and fast point-of-care (POC) test for early diagnosis and amelioration in survival rate. We present a POC test comprising a new vial-immunosensor, a nanoenzyme, and an iPhone 7 plus, which detects and quantifies the new biomarker FXYD domain-containing ion transport regulator 3 (FXYD3) in human urine for specific UCs screening, tumour-grade classification, and postoperative monitoring by the greyscale value of the photo taken. The performance of the proposed POC test was then verified using urine from 4 healthy people, 40 UCB patients (10 patients were low-grade and 30 patients were high-grade), and 13 UTUC patients (2 patients were low-grade and 11 patients were high-grade), confirming the accuracy and specificity by comparing the results with those obtained by enzyme-linked immunosorbent assay (ELISA). Moreover, we also designed a correction method that can make the grayscale values calculated by different smartphones close to the values calculated by iPhone 7 plus, resulting in the POC test enabling simple, fast, universal, and portable testing, data storage and sharing for personal UCs screening and postoperative monitoring.