Andrew Montgomery was appointed Assistant Surgeon on 20 November 1813 and was promoted to the position of surgeon in 1817. 
He was employed as surgeon superintendent on the convict ship Elizabeth in 1820. The Elizabeth departed the Downs 18 August 1820 and arrived in Port Jackson on 31 December 1820.
Philip Parker King's Expedition
Soon after arrival in New South Wales, Andrew Montgomery joined Philip Parker King's fourth and last survey expedition. His appointment to the Bathurst survey vessel was officially announced in England in the newspapers in October 1821, however by this time the expedition was already over....
.....They embarked on the Bathurst, a 170 ton teak built vessel which had recently been considerably repaired at Calcutta. Philip Parker King noted that by this vessel they gained a great addition to their comforts; and, besides increasing the number of their crew, were much better off in regard to boats; for they now possessed a long boat large enough to carry out and weigh an anchor, or save the crew if any accident should happen to the vessel; a resource they had not possessed in the previous vessel the Mermaid. Perceval Baskerville one of the Dromedary's midshipmen joined the expedition and Andrew Montgomery joined the expedition in place of surgeon Mr. Hunter. Others on the vessel included Frederick Bedwell, John S. Roe, and Allan Cunningham - After experiencing many tedious and unexpected delays in equipping the Bathurst, notwithstanding our wants were few, and the greater part of our repairs were effected by our own people, we were not completed for sea until the 26th May, when we sailed from Port Jackson upon our fourth and last voyage to the north coast -
Boongaree, the native who had formerly accompanied us, volunteered his services whilst the vessel was preparing for the voyage, which I gladly accepted; but when the day of the departure drew nigh he kept aloof; and the morning that we sailed his place was filled by another volunteer, Bundell; who proved not only to be a more active seaman, but was of much greater service to us than his countryman Boongaree had been. This addition made our number thirty three.
Three day after we left the port a discovery was made of another addition to the number of the crew. Upon opening the hold, which had been locked ever since the day before we sailed, a young girl, not more than fourteen years of age was found concealed among the casks, where she had secreted herself in order to accompany the boatswain to sea; upon being brought on deck she was in a most pitiable plight, for her dress and appearance were filthy from four days close confinement in a dark hold, and from having been dreadfully seasick the whole time, that her acquaintances of which she had many on board, could scarcely recognise her. Upon being interrogated she declared she had, unknown to all on board, concealed herself in the hold the day before the vessel sailed; and that her swain knew nothing of the step she had taken. As it was now inconvenient to return to put her on shore, and as the man consented to share his ration with her, she was allowed to remain; but in a very short time heartily repented of her imprudence, and would gladly have been re-landed had it been possible.
On 23 June 1821 a boat conveyed Mr. Montgomery and Mr. Cunningham to Clack's Island. The reef abounded with shells, of which they brought back to the Bathurst a large collection.
On 7th August they came across some natives -
By this time Mr. Montgomery and Mr. Bedwell joined us; the latter gentleman was unarmed, but the former had a pistol concealed under his coat, and carried a fish which he held out for them to take; but, as they would not approach us nearer than two or three yards, he threw it towards them, when the shortest native picked it up. Upon this accession to our numbers, they began to talk to each other, and, at the same time, picked up their spears; but, as the latter appeared only to be a cautionary movement, we did not anticipate their mischievous intentions. I then, with a view to amuse them, made signs to my friend for the knife, which he put into my hands without shewing the least reluctance, upon which he was again instructed how to open and shut it; but as this, instead of pacifying, only served to increase their anger, the knife was thrown at his feet, which he instantly picked up, and then both retired a few paces in a very suspicious manner.
We were at this time about three or four yards from the natives, who were talking to each other in a most animated way, and evidently intent upon some object; and, as it appeared probable that, if we remained any longer, a fracas would ensure, it was proposed that our party should retire to the boat, under the idea that they would follow us down; no sooner, however, had we waved to them our farewell, and turned our backs to descend the rocks, than they unexpectedly, and in the most treacherous manner, threw their spears; one of which, striking a rock, broke and fell harmless to the ground, but the other, which was thrown by the tallest man, wounded Mr. Montgomery in the back; the natives then, without waiting to throw their second spears, made off, closely pursued by Bundell, who had armed himself with the broken spear; but they were out of sight in a moment, and, by the time that the muskets were brought to our assistance, were doubtless out of gun shot.
We returned to the boat, to which Mr. Montgomery had been in the mean time carried, complaining of great weakness from loss of blood.
Upon examining Mr. Montgomery's wound, which unfortunately was in such a part of his body that he could not himself inspect it, it appeared that the spear had penetrated about three inches; and, from the quantity of extravasated blood, great fears were entertained that he had received a very serious internal injury.
The wound, from which he was suffering very great pain, was dressed according to his instructions but it was several days before he considered himself out of danger.
Departure from the Colony
Andrew Montgomery departed the colony on the Bathurst with Captain King and family in September 1822