Travis Hager, 20, who police say is homeless, also was arrested for stealing a .22 caliber handgun in an unrelated incident on Feb. 8.
He is charged with four counts of identity fraud, seven charges each of forgery and theft by deception, and one count of theft by unauthorized taking.
The investigation began when Hager's father went to police in mid-January to report the theft.
Det. David Dupont later met with the grandmother JoAnne Hager, 71, of 634 Auburn St. who told him she discovered her credit card was fraudulently used at area ATMs. It happened, she said, after a Christmas Eve visit from her grandson.
She learned someone went online and established a pin number for the card through the company's website.
She also discovered several other personal checks were missing as well.
Police said Hager used the credit card to obtain $940 in cash from ATMs and forged seven of his grandmother's checks and cashed them for just over $1,000 at various banks.
During the investigation, Dupont also identified Hager as a suspect in the Feb. 8 theft of a gun from the 329 Concord St. home of an acquaintance of his.
On Wednesday, police set up surveillance of the 600-block Prescott St. neighborhood after learning Hager was staying in one of the residences. Officers spotted him about 1:30 p.m. leaving one of the residences with several other people. He got into a vehicle which drove off but police pulled it over after it went only several blocks. Hager was arrested without incident.
He was not in possession of the stolen gun, but police said he did have ammunition on him consistent with the .22 caliber handgun.