Laurentius studied first with Þórarinn kaggi, his maternal uncle, in Vellir in Svarfaðardalur and later with Jörundr Þorsteinsson, the bishop of Hólar, and became renowned for his learning.
Following a dispute with the bishop of Hólar, he went to Norway in 1294 and there served Archbishop Jörundr, studying law with Jón the Fleming, and finding himself making enemies among the canons of the cathedral of Nidaros.
The next bishop of Hólar was an old enemy of Laurentius's from among the canons of Nidaros, Auðunn rauði Þorbergsson, with whom Laurentius made peace in the autumn of 1319, going on to teach Auðunn's grandson.
On Auðunn's death in 1322, Laurentius succeeded him as bishop of Hólar, being consecrated in 1324.
Laurentius had a son by a Norwegian woman: Árni Lárentíusson, later a monk at Þingeyraklaustur.