Upon the Moorish invasion in 714, the Bishop of Lamego was forced to flee northbound to the region of Galicia in the northern Iberian Peninsula.

[3] In 876, the first known Bishop of Lamego in nearly 200 years is Argimirus, who was still reigning as late as 899, when he partook in the consecration of the cathedral of Compostela.

In 1143, King Alfonso I of Portugal reestablished the Diocese of Lamego and Mend Godinus, an Augustinian friar, became the new bishop.

[3] On 30 September 1881, Pope Leo XIII by the Bull "Gravissimum" placed the Diocese of Lamego under the metropolitan of the Archdiocese of Braga.

[3] As of 1909, the Diocese of Lamego had 273,741 inhabitants, almost entirely Catholic, 283 parishes, 283 parish churches, 1144 public chapels, 314 diocesan priests, one secondary school for boys run by Benedictines; two convents of Franciscan nuns, and one convent of the Sisters of St. Joseph of Cluny.