Buckingham Palace said Her Majesty has “regretfully decided” she will not attend.
The Palace said in a statement: “Following advice to rest, the Queen has been undertaking light duties at Windsor Castle.
“Her Majesty has regretfully decided that she will no longer travel to Glasgow to attend the Evening Reception of COP26 on Monday, 1st November.
“Her Majesty is disappointed not to attend the reception but will deliver an address to the assembled delegates via a recorded video message.”
The head of state faced preliminary tests in hospital on October 20 during her first overnight stay at a medical facility in eight years.
She has been resting following medical advice to cancel her two-day trip to Northern Ireland.
Her Majesty returned to work on Tuesday when she carried out virtual audiences from Windsor Castle - her first official engagements in seven days.
Sources said the Queen hopes no one will use her absence as a reason to not attend the summit.
It is understood the Queen very much wants COP26 to be a success and result in meaningful action from the participating nations.
Her video message will be filmed later this week.
Sources says it is a “sensible precaution” with regards to resting during COP26.
The Queen wanted to follow advice and to let everyone know in advance.
She remains in good spirits and expects a call with the Chancellor on Tuesday evening as is the norm before the budget.
She will keep to other light engagements in the diary.