Apple has refused to comply with a court order asking it to unlock the device, dividing opinion over whether the firm should be compelled to do so.
McAfee made an "offer" to the FBI to decrypt the information on the San Bernardino phone, free of charge. "We will primarily use social engineering, and it will take us three weeks. If you accept my offer, then you will not need to ask Apple to place a back door in its product, which will be the beginning of the end of America," he added.
The offer came as Mr McAfee continues his campaign as a US presidential candidate for the Libertarian Party.
McAfee also wondered why couldn't the FBI crack the encryption on its own, as it has the full resources of the best the US government can provide.
Chief executive of Apple Tim Cook had previously said in a statement that the firm did not want to co-operate with the U.S. authgorities, as introducing a back door in iOS would make all iPhones vulnerable to hacking by criminals.
Google boss Sundar Pichai has already expressed his support for Mr Cook and yesterday chief executive of Twitter Jack Dorsey added his approval via a tweet.
In a statement, Facebook said it condemned terrorism and had solidarity with the victims of terror, but would continue its policy of opposing requests to diminish security.