The order is for three of the medium twin-engine aircraft and was made under an option to 2010 contract for six of the aircraft. Financial terms of the order weren't disclosed.
The three AW-139s ordered will feature a custom-designed medical evacuation interior.
The AW-139 has a maximum speed of 193 miles per hour, a range of 573 miles and a ceiling of 20,000 feet. It comes in five variants and is used in military and civilian roles around the world.
AgustaWestland said the initial six helicopters ordered by the Maryland State Police are in production in Pennsylvania, with the first scheduled for delivery this year.
"The AgustaWestland team in Philadelphia is proudly building the next generation helicopters for the Maryland State Police," said Robert Brant, vice president of Sales and Marketing. "This order for three additional AW139 helicopters further demonstrates the customers' commitment to our company and our product.
"With significant cost savings over the lifecycle of the program, the new AW139 fleet is a great investment for the state of Maryland."