Hartson recently retired from playing after leaving West Brom and East Stirlingshire had hoped to present the Welshman as their new boss by the middle of this week.
However the 32-year-old rejected the chance to go into management following talks with officials from the Falkirk-based club.
Director Spencer Fearn revealed: "He says he can't accept, but he was very complimentary about the club."
Hartson told The Scottish Sun: "It had nothing to do with the fact that it was East Stirling - if it was the Motherwell job or Dunfermline job I was being offered, I would probably have given the same answer.
"I had loads of friends tell me it would be a great challenge for me and I was sorely tempted to accept the offer.
"But the timing is just not right for me at the moment."
Swansea-based Hartson is not a qualified coach but plans to gain his first badges in the summer with the Welsh FA.