Bar Harbor is about a three-hour drive from Portland and five from Boston, almost all of it on Interstate 95 then US-1A and Route 3 across the bridge to Mount Desert Island. The drive is the standard route.
The small Bar Harbor Airport (BHB) in Trenton, just over the bridge, has summer-only flights from Boston on Cape Air — useful but pricey. The nearest year-round airport is Bangor International (BGR), about an hour's drive northwest. Concord Coach Lines runs a bus from Boston via Bangor in summer.
The Cat Ferry from Yarmouth, Nova Scotia, returned to Bar Harbor in 2022 after a long pause. The crossing takes about 3.5 hours and runs from late May to early October.