Customers can choose seats on the double-decker buses between New York, Baltimore, Washington, Boston and Philadelphia.
The reservation fee ranges from $3 to $7 for trips beginning May 28.
The new service option allows customers to choose from 10 popular seats.
The company will also be adding reserved seating availability on the Toronto-Kingston-Montreal route in the coming weeks with the possibility of adding the option to more routes in the near future.
"We've heard our customers' desires loud and clear," MegaBus vice president of marketing and public relations said. "While every ticket purchase on MegaBus.com guarantees a seat on the bus, we know that customers want to secure some of the most popular seats and, starting today, we're happy to give them that opportunity."
By purchasing adjoining reserved seats, friends and family members will be guaranteed to sit next to each other. Reserved seats are visually distinct with solid blue coloring and are identified by a large number embroidered onto the seat fabric. This number corresponds to the specific seat number customers select at the time of purchase.