Ectopic ureteral orifice presents predominantly in young girls with duplicated kidneys and ureters, and mostly drains from ectopic ureters were associated with non-duplicated upper urinary systems and it is called a single system ectopic ureter. It is frequently associated with renal dysplasia or agenesis and ureterocele. Compared with ectopic ureter draining from the duplicated kidney, the diagnosis of single system ectopic ureter is often delayed because the ectopic ureter may be associated with a single small dysplastic, poorly functioning kidney. We report a case of single system ectopic ureter associated with dysplastic and poorly functioning kidney.