Technology giant Hewlett-Packard confirmed it wants to fill 150 research and development jobs across its Irish operations in Leixlip and Galway.
It is also to create 130 technical and support roles as a result of the expansion.
The company said that the recruitment process will begin immediately.
It said it would be drawing from “Ireland’s deep talent pool to recruit highly qualified engineering and computer science graduates in addition to experienced engineers”.
“The jobs ... solidify Ireland’s strong position at the heart of HP’s commitment to invest in research and development,” said Martin Murphy, HP Ireland managing director.
“Galway and Leixlip are centres of excellence within HP and Irish-based engineers are increasingly developing new leading edge capabilities servicing the needs of clients in the USA, China, India, Europe and Asia.”
In Sligo, Abbott announced it is to invest €85m in the expansion of its pharmaceutical facility, creating up to 175 jobs.
The firm manufactures healthcare products including medical devices, and pharmaceutical, diagnostic and nutritional products.
Abbott said the expansion is designed to support future pharmaceutical developments in the therapeutic areas of virology, oncology and nephrology.
The new posts will be in engineering, quality and pharmaceutical science while the investment will create 150 temporary construction jobs before the site opens in 2014.
In Cork, 30 “highly skilled” jobs are being created by online gaming company Big Fish which is expanding its cloud gaming research and development initiative.
All three companies are US multinationals which are supported here by the IDA.
Speaking in New York where he is attending the “Invest in Ireland” business forum, IDA chief executive Barry O’Leary said: “Today is an excellent day with the forum strengthening Irish- American business links, by highlighting to US business leaders the many advantages of investing in Ireland.
“I am absolutely delighted it coincides with the announcement by three leading US multinationals that they will be investing further in Ireland, creating almost 500 new jobs.”
Meanwhile in Limerick, 60 jobs will be created with the announcement of a new events venue at the University of Limerick.
Masterchefs Hospitality has linked with the university to create the Pavilion which, it says, will dramatically increase the university’s capacity to host events.