Codan Forsikring A/S was established in 1916 by four different companies. In 1940, the company merged with Phoenix Assurance Company Ltd. Later, the group was joined by Fjerde Søforsikring and Hafnia Forsikring (both with substantial marine insurance departments).
- Codan Forsikring A/S was publicly listed in 1964.
- Since 1990, Royal & SunAlliance has held 71,7 per cent of Codan's share capital, making the UK-based insurer the company's largest stakeholder. Royal & SunAlliance is rated A- by Standard & Poor.
- In 1999, the company bought 100% of the Stockholm-based insurance company Trygg-Hansa.
- In 2000 Codan Forsikring A/S together with Trygg-Hansa, established a marine insurance office in Gothenburg.
- In 2001 Codan Forsikring A/S established a marine insurance office in Bergen, Norway, Codan Marine Services A/S.
- In 2001, Codan Forsikring A/S acquired Zurich Marine Stockholm.
- In 2005, the renewal rights of Top Danish AS' marine Portfolio were acquired.
- In 2007, Codan Forsikring A/S acquired Pohjola Marine Helsinki. The same year the Marine division was rebranded to Codan Marine Services to help emphasiste this complete Nordic marine organsiation.
- In 2008 Royal & Sun Alliance changed name to RSA, simplified and refreshed the corporate brand. So did Codan and the Marine division is now working under the name Codan in all Nordic countries.
- In 2010, Codan Forsikring A/S acquired Tryg-Vesta's Nordic marine portfolio.
Since 2007 RSA has owned 100% of Codan & Trygg-Hansa