From 1832 to 1834, he accompanied American merchant and diplomat Edmund Roberts to Siam and Cochin China as his personal secretary and translator.

[4]: p.171  Morrison also compiled a Chinese Commercial Guide to provide information on British trade in China and contributed to Karl Gützlaff's Eastern Western Monthly Magazine,[5] a publication aimed at improving Sino-western understanding.

[6] On 21 August 1843, Hong Kong Governor Henry Pottinger appointed Morrison as Acting Colonial Secretary in the absence of Colonel George Malcolm, and a member of the Executive and Legislative Councils.

In 1840, Walter Henry Medhurst, Karl Gützlaff, Elijah Coleman Bridgman, and Morrison cooperated to translate the Bible into Chinese.

The translation of the Hebrew part was done mostly by Gützlaff from the Netherlands Missionary Society, with the exception that the Pentateuch and the book of Joshua were done by the group collectively.