Ambrosios 1 was primicerius of the notarii (in the Church at Rome); in late 742 or early 743 he was sent with the bishop of Nomentum, Benedict (Benediktos 5) by pope Zacharias (Zacharias 16) to the Lombard king Liutprand 1 with the request to stop attacking Ravenna and to return Caesena to its jurisdiction; the king refused: Lib. Pont. 93. 12 ("per Benedictum episcopum et vicedominum et Ambrosium primicerium notariorum"). In June 743 Ambrosios 1 was again sent by Zacharias 16 to Liutprand 1, this time with the priest Stephanus (Stephanos 78) to announce the arrival of the bishop of Rome Zacharias 16; at Imola, inside Lombard territory, they discovered that the Lombards intended to prevent the pope's journey, and they informed Zacharias 16 of this, by a letter sent secretly under cover of night; Zacharias 16 set out after them, while they went on ahead; when they came to the king Liutprand 1 he refused to receive them, but when the pope Zacharias 16 arrived, reaching the river Po on 28 June (744) Liutprand 1 sent men to meet him: Lib. Pont. 93. 14 ("Stephanum presbiterum et Ambrosium primicerium"). On the orders of the bishop of Rome Zacharias 16, Ambrosios 1 transferred all the pope's wealth into the Lateran palace: Lib. Pont. 93. 18 ("suam substantiam omnem per manus Ambrosii primicerii notariorum introduci mandavit").

In summer 752, in the third month of the papacy of Stephen III (II) (Stephanos 8), Ambrosios 1 primicerius was sent by Stephanos 8 with the pope's brother Paulus (Paulos 49) on a mission to the Lombard king Aistulf 1, who was attacking Rome and its dependent cities, with gifts to try and make peace; they made a treaty of peace with him for forty years: Lib. Pont. 94. 5 ("disponens suum germanum, sanctissimum scilicet Paulum diaconum, atque Ambrosium primicerium"). He was in the retinue of pope Stephen III (II) (Stephanos 8) when it set out from Ticinum (Pavia) on 15 November 753 to visit Pepin 1 in Francia: Lib. Pont. 94. 23 (Ambrosium primicerium). En route at the monastery of St Maurice (St Maurice d'Agaune) Ambrosios 1 fell ill with fever and died: Lib. Pont. 94. 24 (later recension) ("ibi Ambrosius primicerius febre correptus defunctus est").

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