The North British & Mercantile Insurance Company was established in April 1809. Soon after, a notice appeared in the Edinburgh papers announcing a proposal to found a fire insurance company called the North British Insurance Company. In October 1809, a contract of copartnery was submitted and the new company commenced business on November 11. In 1823, the company extended its business to include life insurance.

The company continued to grow and obtained a royal charter in 1824 as its capital was predicted to exceed the one million pounds that was permitted by the contract of copartnery. In 1862 the company merged with the Mercantile Fire Insurance Company, subsequently changing its name to North British & Mercantile Insurance Company. In 1890, the company entered into an arrangement with the Civil Service Insurance Society whereby society members would be insured by North British & Mercantile on certain special rates. This link continued until 1996.