Some 330 jobs are to be created at a Dublin-based postal business and an outsourcing company in Cork.
Private mail firm CityPOST is to take on 180 new staff in a massive expansion of its headquarters in the capital and at its 32 regional bases, while Cork-based SouthWestern is to take on 150 employees in a €3.5m investment.
Jobs Minister Richard Bruton announced the SouthWestern development and warned the country's 14.8pc unemployment rate will only be turned around when business costs are slashed, innovation encouraged and access to finance improved.
"Government does not create jobs, but if job-creating businesses like SouthWestern are to succeed and grow across the country, the Government has a huge role to play," Mr Bruton said.
"We must not only provide supports but must also provide leadership in the economy as a substantial actor in its own right."
CityPOST, a family-owned business run out of Ballymount, will effectively double its workforce over the next 18 months with new staff taken on in mail sorting, delivery and collection, operations and administration.
Managing director Ian Glass said: "We have had a hugely successful year and are braced for even more growth. This sustainable growth has been carefully and meticulously planned for quite some time now."
SouthWestern is to expand its research and development with support from government through Enterprise Ireland.
The company provides outsourcing to public and private sector clients in the Irish, UK and European markets working in agriculture and food, energy, media, insurance and telecoms.
The firm currently employs 450 people in Ireland and 150 at its Polish base in Lodz.
Jim Costello, SouthWestern chief executive, said the company sees great potential for growth in public services, utilities, local government and financial services sectors in Ireland, the UK and central Europe. He also said he wants the firm to play a major role in public sector reform.
"We want to work closely with government agencies to help develop the most effective and cost efficient public services available," Mr Costello said.
"We see today as a launching pad for our future expansion and the expansion of the sector as a whole. It is our ambition to develop world-class services that ensure our growth and enhance the quality and international reputation of Ireland's business process outsourcing sector."