Michael Vaughan's men are due to play five One-day Internationals against the troubled African state in November.
However, Harmison has decided to miss the trip for political and sporting reasons after England officials said they would not hold a withdrawal on those grounds against any player reluctant to tour Zimbabwe.
"In all honesty, my decision was made in Cape Town over 18 months ago when England's World Cup squad spent an horrendous four days before finally deciding not to go to Harare," Harmison told British Sunday tabloid the News of the World on Sunday.
"Nothing has changed for me. The situation there is worse now - that's what the official reports say - and Zimbabwe's top players have been sacked."
England's progress at last year's World Cup was derailed by the controversy surrounding their opening match in Zimbabwe.
They eventually pulled out citing a terrorist threat and the loss of points contributed to the team making an early exit from the competition.
In March the International Cricket Council (ICC) drew up a regulation saying refusal to tour on political grounds could lead to both huge fines and even a suspension from world cricket.
Although many within the game believe this sanction is unlikely to be used against England, a lucrative draw home or away, England and Wales Cricket Board (ECB) officials have said they cannot afford to run the risk of defying world cricket's governing body.
Harmison has become the spearhead of England's attack during the last 12 months, a role that has coincided with him being ranked as the world's number one Test bowler.
He is due to be in England action again in Tuesday's ICC Champions Trophy One-day tournament semi-final against Australia at Edgbaston.