The drive-through, fast-food chain had originally expected to set up shop near Plumtree Road in October 2011, but postponed its construction date after some issues with utilities.
The Facebook page for Sonic of Bel Air said construction is expected to start in February and last about eight weeks, "as long as we don't have too bad of weather."
The restaurant also expects to start hiring employees this month.
The Bel Air location had 1,774 fans on Facebook, as of Sunday. The Facebook page didn't say why the start construction on the restaurant has languished.
Harford County reviewed a site plan for the restaurant last spring. Word that Sonic was planning to move into Harford immediately generated a lot of buzz on Internet sites, including http://www.exploreharford.com.
In May 2011, Sonic regional manager Rick Joshi said he planned to hire close to 100 people. He said the interior of Bel Air's Sonic will look different than existing restaurants and will have two sections inside to look more like a McDonald's. He also said the restaurant would include an outdoor area with four or five tables.
Sonic has four restaurants in Maryland. It offers burgers, hot dogs, chicken sandwiches, smoothies, a breakfast menu and different variations of limeade.