Season four marked the departure of Karen Filippelli as a regular character, although she appeared for a few seconds in the first episode, "Fun Run" and in the sixth episode, "Branch Wars", as the regional manager of the Utica branch. Relationships again emerged as the main theme of the season, with Jim Halpert and Pam Beesley's rising, and Michael Scott and Jan Levinson's, as well as Dwight Schrute and Angela Martin's declining. Technology was another prevalent theme as the office staff struggled with initiatives introduced by Ryan Howard to modernize the company.

The season marked the move of main character Jim Halpert from Scranton to Stamford, and also introduced Rashida Jones as Karen Filippelli, and Ed Helms as Andy Bernard—both members of Dunder Mifflin Stamford—as recurring characters. The main plot for the early episodes of the season deals with a recurring problem in seasons one and two—the problem of company downsizing—while in the last half of the season, inter-office relationships also became a major plot point.