Sales rose 0.9% month-over-month, and 8.3% year-over-year.
Economists had estimated that pending sales rose 1.1% month-over-month, a slowdown from 3.4% in April, according to Bloomberg. Year-over-year, they forecast an 11.8% rise.
The data from the National Association of Realtors include transactions in which a contract has been signed, but not yet concluded.
In a weekly preview of the economy, Bank of America Merril Lynch wrote: "This measure of home sales has been rising steadily since January despite the harsh winter weather. This therefore set up for a solid selling season. The improvement in pending home sales has been supported by a gain in mortgage applications and new home sales."