With only one very economical exception, the park is free. You do have to pay a $1 admission to climb the lighthouse during the summer (from Memorial Day weekend through Labor Day). Children under 12 are always allowed to visit for free but they must be accompanied by an adult.
There are 217 steps that lead to the light. From there you can see a long ways on a clear day. If you are familiar with this area of the Jersey shore and have never seen the area from up high, the view from the lighthouse will be even more special. In all areas of the lighthouse you will find interpretive signs that discuss the history and role of lighthouses, in addition to specific details about the Barnegat Lighthouse itself.
The lighthouse is open (weather permitting) every day from April 1 through October 31, 9 a.m. to 4:30 a.m. From April 1 through October 31 it is open from 9 AM to 3:30 PM, Wednesday through Sunday.
There is a long list of folks that should not climb the lighthouse. Be sure you are Ok with the strenuous nature of the climb. If you cannot or do not want to walk to the top you can still see the view from cameras.