I-395 primarily serves as a bypass of Bangor and Brewer for travelers wishing to access the Downeast/Bar Harbor region of Maine. As such, travelers exiting I-95 can easily access US 1A without having to traverse the business districts of Bangor and Brewer, and are less than 40 miles from Bar Harbor where I-395 terminates at US 1A.
I-395 begins at a cloverleaf intersection with I-95, and travels primarily east-west although not in a straight line. It has interchanges with US 202, Main Street in Bangor (which is US 1A), and then crosses the Penobscot River. It then has an interchange with S. Main Street in Brewer (ME 15), and then Parkway South (this interchange was the previous terminus of the highway until it was extended to US 1A later on). I-395 finally comes to an end at US 1A which is also known as Wilson Street. From there, travelers can choose to go east towards the coastal cities of Ellsworth and Bar Harbor, or west towards Brewer and downtown Bangor.
There are studies underway about extending I395 to connect to SR 9. In February 2008, the Maine Department of Transportation (MaineDOT) suggested five possible routes to extend I-395 to SR 9, with two in particular designated as "State's Choice" and "Holden's Choice". The state's choice route would cut through the middle of Holden and connect to SR 9 in East Eddington; Holden's choice would run along the Brewer–Holden border and join SR 9 earlier. Since then, the state has eliminated the "State's Choice" route and only supports the "Holden's Choice" route, designated 2B-2. All three affected communities issued resolutions in 2014 opposing this route.