Guðmundsson was born on 6 October 1888 in Reykholt, Iceland.

He graduated from the University of Iceland on 19 June 1912.

He served as pastor to the Icelandic settlements in Alberta for a month in 1914 and in Saskatchewan in Canada from 1912 till 1914.

Appointed principal of Eiðar on 11 January 1919 and Associate Professor at the Faculty of Theology at the University of Iceland on 24 April 1928 and Professor on 24 April 1934.

Ásmundur Guðmundsson wrote a number of books, including The Supreme Life (1964) about Jesus' life.