The world's largest retailer agreed Monday to buy the online shopping site Jet.com for about $3.3 billion.
The online retailer site has been in operation for more than a year, and has reached $1 billion in run-rate gross merchandise value. It also has a growing customer base of urban and millennial customers.
The deal might help strengthen growth in Wal-Mart's online business. Wal-Mart has seen slow growth online and trails far behind Amazon as the second-largest online retailer.
"When you have a blank check this is what you put on it … you put $3 billion to Jet.com," Cramer told CNBC's "Squawk on the Street." "And the [Walton] family won't [ask] any questions, cause the family said, this Amazon ... you have to take them on."
The Walton family, the kin of the founders of Wal-Mart, holds a collective majority of the stock.
"Wal-Mart was the 'sleeping giant,'" Cramer said, "and they're awake."
Wal-Mart said the deal is expected to close this year, subject to regulatory approval.
Both Wal-Mart and Amazon shares were trading slightly lower Monday.