Pfizer is creating about 300 jobs at its manufacturing sites in Grange Castle in Co Dublin, Newbridge in Co Kildare and Ringaskiddy in Co Cork.
The US drugs company said it is investing about €300m in its Irish operations to support the further development of the three sites.
The investment and hiring of the new jobs will be completed over the next two to three years.
In separate jobs announcement today, Domino's Pizza said it is creating 715 jobs across the country, including new management positions, team members and contract drivers.
Domino's already provides work for nearly 2,000 staff and contract workers across its 85 Irish stores.
Elsewhere, a US firm that provides communication software to hundreds of international companies is also to create 200 jobs in Galway.
Diligent Corporation specialises in secure, end-to-end, corporate governance software.
Pfizer has been operating in Ireland since 1969 and has 4,000 workers across six locations based in Cork, Dublin, and Kildare.
The new roles include comprise a broad range of highly skilled positions including analysts, technicians, engineers, scientists, technologists, quality specialists, data analysts and chemists.
Pfizer said its latest investment will upgrade and enhance its facilities, expand manufacturing and laboratory capacity and add new technologies to ensure it is ready to support the next wave of medical innovations.
It said that part of the investment includes the initial stage of a project to construct a development facility on its existing Ringaskiddy site to manufacture pharmaceutical compounds for the company's clinical trials globally.
"This is a very important development as it expands Pfizer's role in Ireland from the manufacture of already approved medicines into supporting the earlier phases of new medicine development," the company said.
Pfizer's Irish sites manufacture medicines and vaccines in the areas of arthritis, inflammation, cancer, anti-infectives, haemophilia, pain and stroke.
Paul Reid, Country Manager of Pfizer Healthcare Ireland, said the company's purpose is to discover breakthrough medicines that change patients' lives.
He said these new positions are key roles within the organisation and play an important function in the manufacturing and delivery of medicines to patients worldwide.
"Currently we are focused on our Covid-19 efforts, including our vaccine development programme. Pfizer is also significantly investing in other innovations across healthcare such as gene therapy and complex biologics targeting some of the most debilitating medical conditions," Mr Reid said.
Dr Paul Duffy, Vice President of Pfizer Global Supply, said pharmaceutical manufacturing here continues to perform very well.
"Pfizer has an extensive global and U.S. footprint with operations in over 125 countries worldwide and we are very pleased with today's announcements which will strengthen our Irish operations and bring our total headcount in Ireland to 4,000," he said.
"It is also particularly exciting that our Ringaskiddy site has been chosen as the location to manufacture investigational compounds for our clinical trials globally and we look forward to seeing that new facility become operational."
Taoiseach Micheál Martin said today's significant jobs and investment announcement by Pfizer is a further vote of confidence in the skills and talent of Irish people and provides a very welcome boost to the economy.
"Over the past five decades, there has been a huge expansion of the sector in this country, creating thousands of jobs and solidifying Ireland's reputation as a world leader in pharmaceutical innovation and manufacturing," Mr Martin said.
"Pfizer has made a significant contribution to the Irish economy and this latest investment is a testament to the quality and experience of the workforce here," he added.
Martin Shanahan, the CEO of IDA Ireland, said today's investment announcement and the substantial number of additional highly skilled roles across its three Irish sites is a huge vote of confidence in Ireland's investment environment.
Mr Shanahan said it again underscores Ireland's reputation as a global location of excellence for biopharmaceuticals.
Pfizer hopes to be the first US drugmaker to announce successful data from a late-stage Covid-19 vaccine trial.
The company along with its German partner BioNTech launched their 44,000 volunteer phase 3 study of their vaccine in late July.