In 1835 the French Academy sent Antoine on a scientific mission to Brazil, the results being published at a later date (1873) under the title of Observations relatives à la physique du globe faites au Bresil et en Ethiopie. The younger Abbadie spent some time in Algeria before, in 1837, the two brothers started for Abyssinia, landing at Massawa in February 1838. They visited various parts of Abyssinia, including the then little-known districts of Ennarea and Kaffa, sometimes together and sometimes separately. They met with many difficulties and many adventures, and became involved in political intrigues, Antoine especially exercising such influence as he possessed in favour of France and the Roman Catholic missionaries. After collecting much valuable information concerning the geography, geology, archaeology and natural history of Abyssinia, the brothers returned to France in 1848 and began to prepare their materials for publication. The younger brother, Arnaud, paid another visit to Abyssinia in 1853.
The more distinguished brother, Antoine, became involved in various controversies relating both to his geographical results and his political intrigues. He was especially attacked by C. T. Beke, who impugned his veracity, especially with reference to the journey to Kana [Kaffa?]. But time and the investigations of subsequent explorers have shown that Abbadie was quite trustworthy as to his facts, though wrong in his contention--hotly contested by Beke--that the Blue Nile was the main stream. The topographical results of his explorations were published in Paris in 1860-1873 in Geodesie d'Ethiopie, full of the most valuable information and illustrated by ten maps. Of the Geographie de l'Ethiopie (Paris, 1890) only one volume has been published. In Un Catalogue raisonné de manuscrits ethiopiens (Paris, 1859) is a description of 234 Ethiopian manuscripts collected by Antoine. He also compiled various vocabularies, including a Dictionnaire de la langue amarinna (Paris, 1881), and prepared an edition of the Shepherd of Hermas, with the Latin version, in 1860. He published numerous papers dealing with the geography of Abyssinia, Ethiopian coins and ancient inscriptions. Under the title of Reconnaissances magnetiques he published in 1890 an account of the magnetic observations made by him in the course of several journeys to the Red Sea and the Levant. The general account of the travels of the two brothers was published by Arnaud in 1868 under the title of Douze ans dans la Haute Ethiopie.
Both brothers received the grand medal of the Paris Geographical Society in 1850. Antoine was a knight of the Legion of Honour and a member of the French Academy of Sciences. He died in 1897, and bequeathed an estate in the Pyrenees, yielding 40,000 francs a year, to the Academy of Sciences, on condition of its producing within fifty years a catalogue of half-a-million stars. His brother Arnaud died in 1893.