Snelling won 82 percent of the vote in defeating Mike Miller, a Douglas County School Board member.
The Douglasville resident will now face Kimberly Alexander, who was unopposed in the Democratic primary, in November for election to the seat.
Snelling previously served in the state House from 1994 to 2002. He opted not to seek re-election when then-majority Democrats paired him with another Republican House member during redistricting following the 2000 federal census.
House District 66 was formed during redistricting following the 2010 federal census.
Also Tuesday, College Park attorney LaDawn "LBJ" Jones defeated Marvin Arrington, an Atlanta attorney, in the runoff for the Democratic nomination for the House District 62 seat.
Jones received 63 percent of the vote and Arrington 37 percent.
The runoff victory was tantamount to election to the District 62 seat. Jones will be unopposed in the Nov. 6 general election.
District 62 includes parts of Douglas and Fulton counties.