Eighteen of the alleged victims are Ottawa residents while the others are from elsewhere in Canada, the United States and the United Kingdom, Ottawa police said Friday.
The charges follow an eight-month investigation dubbed Project Winter.
"This individual stole individual's identities, posted defamatory comments and other material online that affected all these victims not only personally, but also professionally," said Carl Cartright, acting inspector with Ottawa police.
It's alleged the activity began around 2001 with the man targeting people he knew, then preying on his alleged victim's acquaintances as he gained more experience, Cartright said.
He said the techniques became more sophisticated over time, with the suspect using software to cover his tracks, which proved a challenge for investigators.
"As the victims came forward, police forces had to identify a common link," Cartright said.
"The spider web, at the end, it must lead to a centre. At the centre of this web was our accused."
A search warrant was executed Thursday at a west-end residence in Ottawa.
Robert Campbell, 42, faces 27 counts of criminal harassment, 85 counts of defamation libel and 69 counts of identity fraud.
The investigation also involved RCMP, Ontario Provincial Police, police in Vancouver, Halifax, Central Saanich, B.C., Rothesay, N.B., and Ferndale, Mich., as well as London Metropolitan Police and the Hertfordshire Constabulary in the U.K.