Dúngal appears to have settled in Pavia by 811, when a scholar of that name sent Charlemagne a dissertation on the two solar eclipses of the previous year. He complains of the lack of certain works on astronomy which would have helped him to elucidate the subject more fully. In May 825 Dúngal is referred to in a capitulary of Lothair I, the ‘Constitutiones Olonnenses’, in which Lothair states his intention of restoring learning in his kingdom, and names Dúngal as master of the cathedral school of Pavia: ‘in Papia conveniant ad Dungalum’. In 827 Dúngal wrote a tract, ‘Responsa contra perversas errores Claudii . . .’ (attacking the fundamentalist teachings of Claudius of Turin opposing the veneration of images). His part in the iconoclastic controversy between Louis the Pious and the eastern emperor Michael II earned him a degree of notoriety. Around 829, a poem by Bishop Donatus (qv) of Fiesole was addressed to a certain Dúngal, whom Mario Esposito (qv) has identified with Dúngal of Pavia. The metrical Life of St Brigit (qv) by Donatus may also have been dedicated to him.
It seems that Dúngal eventually retired from Pavia to Bobbio, bringing his library with him. The old catalogue of the library of Bobbio, dating from the ninth or early tenth century, lists twenty-nine manuscripts (nos 480–508) which were donated to the monastic library by Dúngal. It describes the donor as ‘Dungal, that eminent scholar of the Irish’. Six of the manuscripts still survive, two of which have annotations in Dúngal's hand: Milan, Bibl. Ambr. C.74 sup., and Leiden, Voss. lat. F.30 – the famous ‘Codex oblongus’ of the Latin poet Lucretius. Nothing definite is known of Dúngal after 827; he probably died in the early 830s.