Aetna Inc. Chief Executive Mark T. Bertolini is set to pocket roughly half a billion dollars when he leaves his company if it successfully merges with CVS Health Corp.

If the $69 billion deal between the pharmacy chain and health insurer goes through, Mr. Bertolini stands to reap a generous exit payment and benefit from a sizable increase in the value of the stock and rights he owns because of the premium CVS is paying for Aetna. His combined payout is expected to be about $500 million, according to people familiar with the...