That's triple expenditures from the same period in 2017, when Google posted expenditures of $2.409 billion, and double expenditures for the fourth quarter of 2017, when Google spent $3.805 billion.
The spike demonstrates the company's "commitment to growth," CFO Ruth Porat said on the earnings call.
Analysts had expected just $3.5 billion in capital expenditures for the first quarter for all of Alphabet's divisions.
Data centers and other facilities represented a key driver of costs, Porat said. Google also completed a $2.4 billion purchase of New York's Chelsea Market last month.
"Our facilities spend in Google, dominated by the Chelsea Market acquisition, reflects that we favor owning rather than leasing real estate when we see good opportunities," Porat said. "We are also investing in data center growth and increased network capacity through undersea cables."
Content acquisition for YouTube and hardware-related costs also drove expenditures up, Porat said.
— CNBC's Jordan Novet contributed to this report.