[1] Geir was the son of Jón Jónsson a priest in Laufás, and Sigríður Magnúsdóttir.

He graduated from the University of Copenhagen in 1789 and became a cathedral priest in Reykjavík and lived in Lambastaðir at Seltjarnarnes.

He was elected Bishop of Skálholt after the death of Hannes Finnsson in 1796.

He was consecrated by the Bishop of Hólar Sigurður Stefánsson on 30 July 1797.

After the death of Stefánsson, no new successor was appointed to Hólar and the two Icelandic dioceses were amalgamated into the united Diocese of Reykjavík in November 1801, with Geir Vídalín as the first bishop.