Leif Johansson said that AstraZeneca had engaged with shareholders over the bid and was happy that the decision to reject the deal was the right one.
Pfizer has pursued its U.K. rival for months, in its attempt to create the world's largest drugs company. On Monday, AstraZeneca's rejected the U.S. giant's "final" bid of £69 billion ($116 billion), worth £55 per share.
The move saw shares in AstraZeneca drop by up to 13 percent on Monday, however, and by late-afternoon London time, shares were down 11 percent at £42.87. Pfizer shares traded 1.3 percent higher.
"We have engaged with shareholders all through May so I think we are reasonably confident … it is the right move," said Johansson.
"If shareholders aren't happy with that then we need to continue to engage with them and continue what we are doing… shareholders have the right to vote me away."