A call centre is creating 250 jobs in the south east.
Eishtec, which was set up after TalkTalk shut its call centre in Waterford two years ago, said it would expand its workforce from 700 to 950 by next year.
The company was founded by former employees of the collapsed TalkTalk enterprise and has grown from just nine employees in May 2011.
Heather Reynolds, co-founder of Eishtec, said they have not been entirely surprised by the quick expansion.
"Our company mission is to challenge the standards of service," she said. "Therefore at Eishtec we have a particular approach to providing customer service that delivers a performance and experience that our clients, and their customers, love."
The latest jobs announcement is being supported by the taxpayer-funded Enterprise Ireland.
The new roles will be at the company's offices in Waterford and Wexford.
Jobs minister Richard Bruton said more Irish companies need help to start up, export more, grow faster and create more jobs.
"This is an Irish company started in 2011, growing rapidly in export markets, and deriving its success from the ingenuity of its founders, the quality of the staff and the support of Government and the local community," he said.
"In the south east, as across the country, we have a long way to go but we can have confidence that we are on the right path."
The jobs were made possible after a new contract was secured to support UK mobile company T-Mobile.