The MTA Police Department held a graduation ceremony Wednesday for 19 dogs.
The canines completed the agency's bomb-detection and anti-terrorism courses.
Fifteen will protect the Staten Island Railway, Metro-North and the Long Island Railroad.
The four others will join the United States Park Police and the Putnam County Sheriff's Office.
The dogs are named in honor of fallen police officers, firefighters and members of the Armed Forces.
Some of their family members attended the ceremony.
"Oh my God, he would have loved it," said Marge Dwyer, the mother of a slain NYPD officer. "He loved dogs. He loved animals. He loved people. He would have been in his glory to see this today. I'm sure he's watching us."
"Safety and security is MTA's number one priority," said MTA Police Chief Michael Coan. "The newly graduated canines will soon be on patrol keeping our customers and employees safe."
Last year, dogs from the MTA canine explosives detection unit responded to more than 25,000 cases and inspected close to 26-hundred unattended packages.