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“It had generally been assumed that [Amazon’s] growth would be concentrated in Seattle,” said Dave Bragg, an analyst with Green Street Advisors, a real-estate research firm. “That now needs to be adjusted.”

Green Street, in a new report titled “Sleepless in Seattle,” lowered its 2018-21 growth estimate for the city’s office sector by an average of 1.5 percentage points. In the near-term, growth is expected to be “modestly” slower in the apartment, industrial and strip-center sectors, the report says.

When Amazon announced its search for a second headquarters last month, the company said it expects to invest more than $5 billion in the new location and create up to 50,000 high-paying jobs.

Amazon hasn’t said how the move will affect its plans for growth in the Seattle area. Before the announcement, the company had said it expected to add another 2 million square feet of office space to the 8.1 million square feet it currently occupies across 33 buildings in the city.

“Uncertainty surrounds Amazon’s previously reported leasing and construction plans,” Green Street noted in its report.

Real-estate experts believe Amazon’s decision might inflict more harm to Seattle area growth than Boeing Co. did when it moved its corporate headquarters to Chicago in 2001. Boeing moved “a few hundred headquarters jobs” but maintained most of its manufacturing operations in the Seattle area, noted Simon Stevenson, chairman of the real estate department at the University of Washington.

In technology businesses, the distinction between manufacturing and headquarters jobs “is a lot more blurred,” he said. “You could see a lot more movement of staff.”

Mr. Stevenson also pointed out that the Amazon move coupled to the earlier Boeing decision might create an image problem for Seattle among businesses considering locating there. “At what point do people start thinking it’s a Seattle problem,” he said.

Seattle has had one of the strongest real-estate markets in the country in recent years. Commercial property values there have doubled since 2010, compared with a 61% increase in the top 50 markets tracked by Green Street.

Amazon is responsible for as many as one-third of the jobs created there since 2010, according to Green Street. About 40,000 people worked for Amazon in the Seattle area at the end of 2016, Mr. Bragg said, up from 4,000 in 2010.

Another 53,000 jobs can be indirectly tied to the company, he added.

That growth has had a multiplier effect throughout the regional economy, boosting residential prices, retail rents and demand for other property. “Amazon has had a massive impact on Seattle’s outperformance,” Mr. Bragg said.

The Seattle economy is now being stoked by demand from a range of other companies like technology firm F5 Networks Inc., which leased more than 500,000 square feet in the city in the second quarter. The Puget Sound’s office vacancy rate was 11.3% at the end of the quarter, compared with around 16% in 2012, according CBRE Group Inc.

Amazon hasn’t said why it is expanding its growth beyond Seattle.

But the Green Street report speculates that a shift in the city’s regulatory climate might have played a role in the company’s decision to expand elsewhere. For example, Seattle recently approved an income tax on wealthy households, a move that is being challenged in court.

“It’s not too hard to connect the dots,” Green Street’s Mr. Bragg said.