Brown said earlier this week that Nevada and Arizona's looser gun laws are "a gigantic backdoor through which any terrorist can walk."
The Democratic governor was responding to some California lawmakers' call for tightening the state's already strict gun laws.
In a statement Sunday, Sandoval spokeswoman Mari St. Martin called Brown's characterization "wrong and irresponsible."
St. Martin says his "political rhetoric is discouraging to hear at a time when all Americans are looking for thoughtful, honest leadership."
She says the Republican Sandoval has always made safety a top priority.
The San Bernardino attackers purchased some of their weapons legally in California.
On Saturday night, Arizona Gov. Doug Ducey criticized Brown's comments. In a statement, the Republican said, "All of Arizona mourns for the victims in California. Not only will we be ignoring Gov. Brown's advice, but I call on him to retract his incredibly thoughtless and ill-advised comments."