The case of Steven Redford, who worked at the Albany Lodge acute inpatient unit in St Albans, was heard by the Nursing and Midwifery Council (NMC).
The hearing found that he had a sexual relationship with a female patient between January and March 2011.
The NMC found Mr Redford's actions amounted to misconduct.
The NMC panel heard evidence from the woman known as Patient A, a patient with mental health problems at Albany Lodge.'Not a liar'
She described how Mr Redford had begun a relationship with her while he was a nurse at the unit.
The report of the panel said: "Patient A stated that she only had 'full sex' with Mr Redford on one occasion. Although she said that they did 'everything else' and although she wanted to go out on a date he just wanted to have sex."
A doctor told the hearing he was certain the patient was "not a liar" and the panel accepted Patient A was a reliable witness.
The report said Mr Redford chose not to attend the hearing and did not cross-examine witnesses.
The panel concluded that: "Mr Redford's actions were significant departures from the standards expected of a registered nurse, and are fundamentally incompatible with him remaining on the register.
"The panel of of the view that the findings in this particular case demonstrate that his actions were serious and had a significant detrimental effect on those in his care."