The 35-year-old was approximately 30 nautical miles off the coast of Lagos, Algarve (Southern Portugal) when the alarm was raised.
He was struggling in rough seas and the 7-metre-long rowing boat was taking on water.
He was located by Portuguese authorities in the afternoon on the Diligente rescue boat, and brought back to Baleeira port in Sagres, where he arrived close to midnight.
Assistance was also asked of merchant navy ships in the vicinity, as well as from a Maltese vessel, which had located the rowing boat and kept an eye on it until the Diligente arrived.