The woman has made a full recovery, and it is thought she had been infected by her partner, who had recently visited a Zika-hit country.
Mostly spread by mosquitoes, Zika can linger in semen for months.
Cases of sexual spread have been reported in other countries and experts said the UK case was "not unexpected".
An update by Public Health England said there had been 265 cases of Zika in the UK with one "likely" spread through sex.
Seven cases were in pregnant women.
While Zika is normally a mild infection, it can damage the development of a baby's brain, leading to microcephaly.
Earlier this month the World Health Organization said Zika virus will no longer be treated as an international medical emergency. By lifting its nine-month-old declaration, the health agency acknowledged that Zika was here to stay.