Isaias Grandis grew up in the Welsh-speaking part of Argentina but said he found it hard to understand the accents when he first came to Wales in 2006.
He beat finalists Ashok Ahir, from Cardiff, Mark Morgan from Pontyclun and Rhian Dickenson, from Abergavenny.
The finalists were:
Ashok Ahir: Aged 42, the the former managing editor of BBC Wales’ political unit. He began learning Welsh in 2005. A co-chair of governors at two Cardiff Welsh-language schools, he interviews staff in Welsh.
Rhian Dickenson: She is head of Welsh at Abergavenny’s King Henry VIII School, and teaches Welsh as a second language to A-level standard. Brought up in Gilwern, she started learning Welsh at school.
Isaias Grandis: A native Spanish speaker, he became interested in the “foreign” language he heard neighbours speak after his family moved to the Welsh-speaking area of Patagonia. He began learning Welsh at 15.
Mark Morgan: The 39-year-old is a a Regimental Sergeant Major in the British Army. He realised he had to learn the language when he and his wife Ceri decided to bring up their two sons in Welsh. He continued studying during a tour in Afghanistan in 2007.
I love the Eisteddfod and really enjoyed as a child trying to enter the competitions and waiting for it to come to a town near me. This did not happen until I was more of an adult but the love of poetry and singing is very much in my heart. It is therefore great to see a young person winning the Welsh Learners Medal….keeping Welsh alive.
The number of visitors was up from 20,083 on the second day of competing in 2011, and bigger than Monday’s attendance figure despite the poorer weather.
But speaking before presenting Nia Haf Jones with the Welsh Learners’ Medal on the stage of the main pavilion, guest president and author Angharad Tomos spoke of her hopes for the future of the language.