The Office's showrunner Greg Daniels revealed last week that the sitcom will come to an "exciting" end in 2013 after nine seasons.
Fischer - who plays Pam Halpert on the series - revealed to Us Weekly that she is very emotional about the approaching end of The Office.
"We're already getting very sentimental," Fischer said, adding: "We are cherishing every moment, every scene already and we're only on the fourth episode."
She added: "We're really enjoying ourselves… Oh my God, a lot of laughter and a lot of tears. I think that will describe the next few weeks of our lives."
Fischer also predicted that Office fans will be satisfied with the way the series concludes.
The actress explained: "The writers worked very hard and are working very hard to give every single character a very fitting end to the series. And I know a lot of the plans for a lot of the characters and I couldn't be happier.
"They have something planned for each person, to really celebrate their character's contribution to the show."
The final season of The Office will also launch the spinoff The Farm, which will centre on Dwight Schrute (Rainn Wilson) and his family's beet farm.
The Office returns on Thursday, September 20 at 9/8c on NBC.