At the end of the first quarter, Uber reported having 24,494 workers worldwide, with more that 1,200 of them in marketing.
Khosrowshahi in June tightened his grip on the wheel at the ride-hailing firm in the wake of a bumpy stock market debut.
Hazelbaker took charge of the marketing department, while Uber's chief operating officer and head of marketing left in a leadership shake-up that resulted in Uber's shared rides and food delivery platforms reporting directly to Khosrowshahi, according to a copy of an internal email provided to AFP.
As a factor in the marketing, communications and policy consolidation, Khosrowshahi cited a need for a clear and consistent "narrative" at Uber for how the company is seen by consumers, partners, policymakers and the press.
After debuting in May at $45 for the initial public offering -- translating to a market value of $82 billion -- Uber shares went into reverse.
Its rival Lyft earlier in the year saw its shares fall after a market debut. Uber shares were $43.88 at the close of formal trading in New York on Monday.
In its first earnings report as a publicly traded company, Uber said revenue climbed to $3.1 billion in the first quarter of this year, but that it lost $1 billion.
Uber is to report second-quarter earnings next week.
While the firm has lost billions since offering its first rides in 2011 in its home city of San Francisco, it envisions becoming the "Amazon of transportation" in a future where people share instead of owning vehicles.
The company has moved into electric bikes and scooters, as well as meal deliveries and has a long-term project on flying taxis.