The 41-year-old leader of Fine Gael will carry out one session a week for the Health Service Executive.
Dr Varadkar qualified as a GP after studying medicine at Trinity College Dublin.
He left the Irish Medical Council register in around 2013 after his political career took off and was appointed Taoiseach after winning the leadership of Fine Gael in 2017.
However his registration is now listed as active on the Irish Medical Council.
Fine Gael confirmed that the Taoiseach had rejoined the medical register last month as Covid-19 began to hit the country.
“He has offered his services to the HSE for one session a week in areas that are within his scope of practice,” a party spokesperson said.
“Many of his family and friends are working in the health service. He wanted to help out even in a small way.’
It follows pleas from the Irish government to retired or unregistered doctors to return to the profession to help with the fight against the pandemic.
Several British MPs have responded to similar calls in the UK, including Conservative Maria Caulfield, a registered nurse, and Labour’s Rosena Allin-Khan, a doctor.
Dr Allin-Khan, who is helping her local A&E department, told The Independent: “I’m proud to pull on my scrubs and get stuck in alongside my phenomenal NHS colleagues, especially when I’m inundated with messages of concern about the conditions they are having to work in.”
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