Lake County, where a tornado damaged homes and businesses in Merrillville, is among those included.
Porter, La Porte, Jasper and Newton counties are also included in the disaster declaration.
The governor says this will ensure state resources are mobilized quickly to help families and local governments recover.
Indiana has been hit by several rounds of strong storms over the last week and a half.
On Wednesday, a tornado outbreak that injured several in Effingham, Illinois also caused damage in Indiana.