Alexander began his career in India when he arrived at Fort St George, Madras, in 1752, at the age of twenty-three, and became a factor there.
In a letter of introduction to someone in Madras, through which he passed in January 1767, he was described (significantly) as 'Coja Alexander' - coja meaning a wealthy merchant: '...
Marshall has written: "[Among the great fortunes which were amassed in Bengal before the end of the 1760s] ... were [those] made by Francis Sykes, Thomas Rumbold and James Alexander, who had all taken a rich harvest out of the early revenue administration, Sykes as Resident at Murshidabad, Rumbold at Patna, and Alexander at both.
James Alexander had already acquired property nearer his native Derry: the house and demesne of Boom Hall, outside the city, the Churchland estate of Moville, County Donegal, and a fee simple estate near Ballycastle, County Antrim.
Alexander was a staunch Tory in his politics and had spent the staggering sum of over £600,000 on acquiring estates in Ireland, including the parliamentary borough of Newtownards in County Down, and became a strenuous supporter of the Act of Union.