Andy Briggs, head of Aviva's UK life business, will take on general and health insurance to become the chief executive of the UK Insurance business, Aviva said in a statement.
Briggs was formerly chief executive of Friends Life, which Aviva acquired in 2015.
Maurice Tulloch will become CEO of International Insurance, responsible for the firm's operations in France, Canada, Ireland, Spain, Italy, Poland, Turkey and India.
Aviva has been pulling out of some international markets in recent years.
As a result of the changes, David McMillan, chairman Aviva Global Health Insurance and CEO Aviva Europe, has chosen to leave the firm, Aviva added.
Aviva, which is unusual among UK listed insurers in having large operations in both life and general insurance such as home and motor, is focusing more on its digital business, offering a range of life and general insurance products online.
"We see significant opportunities to differentiate our business in the UK post-Brexit," group chief executive Mark Wilson said in a statement.
“Our priorities are to continue to deepen our position in our home UK market...and to continue to grow in our core international markets."
Aviva's shares were trading at 474 pence at 1040 GMT, down 1.0 percent on the day and underperforming the FTSE 100 index <.FTSE>.
"I don't think Aviva has made any secret of the fact that they would like to have a better track record in cross-selling," said Eamonn Flanagan, analyst at Shore Capital, which has a neutral rating on the stock.
"This structure makes sense."
(Reporting by Carolyn Cohn and Noor Zainab Hussain; editing by Simon Jessop and Elaine Hardcastle)