BBC Radio Cymru's Shân Cothi sang the Welsh hymn Calon Lân with Andres Evans.
The record-setting link-up, officially "the greatest distance between people singing a duet", was broadcast live on Radio Cymru for BBC Music Day.
It is one of a number of projects marking the 150th anniversary of the establishment of a Welsh settlement, Y Wladfa, in Patagonia in 1865.
A duet bridging the 7,000 miles between Wales and Patagonia has set a new world record.