Ashraf Ghani, a former finance minister, was sworn in as president on Monday, ending the stand-off with Abdullah, an ex-foreign minister, over who won the vote. Stability will now depend on how well the alliance holds.
The new president is an ethnic Pashtun with a support base in the east and south of the country, while Abdullah is backed by Tajiks, who make up most of the population in Panjshir and other northern areas.
As part of the U.S. brokered agreement, Abdullah has become chief executive, a similar role to that of a prime minister, and will share control over key government decisions.
But in Panjshir, governor Abdul Rahman Kabiri said people were worried Abdullah would be pushed out of power.
"Panjshiris are watching the situation," Kabiri told Reuters in an interview. "If they don't commit to the agreement, people will demonstrate."
Abdullah is backed by many Panjshiris because of his close ties to their beloved leader Ahmad Shah Massoud, who was assassinated in 2001 and is remembered as a national hero.
Cracks in the deal to share power have already emerged, with Abdullah's camp nearly boycotting the swearing-in ceremony, Reuters reported.
On the streets of Panjshir, sentiment was a mixture of resignation and anger. One shopkeeper said he ripped up his voter card after Ghani was declared the winner.