Upon his father's death in 1790 he became head of James Finlay & Co, manufacturers and East India merchants.

They became the largest textile concern in Scotland and the first British merchant to trade directly with India (1816).

[1][2] Whilst developing James Finlay & Co. into the leading merchant firm of its time he also led a very active public life.

He was part of the abortive scheme to raise a joint-stock bank in Glasgow around 1793, he agitated for the retention of the Scottish one pound note in 1826 (appearing before the House of Commons Committee on Promissory notes in Scotland and Ireland), and was also active in opposing the changes to factory conditions in 1833.

In 1820, unfounded rumours spread around the university that he was building up a motion to disallow student voting at rectorial elections.