The proposed job losses – a total for which have not been specified by the company – follows a major review of its manufacturing operations in Ireland over the past year.
Pfizer employs over 5,000 people in Ireland in manufacturing, sales, administration, logistics and research & development.
It is understood up to 200 jobs are involved in the cutbacks and will be spread across all three of its major manufacturing sites in Ireland.
The job losses are being sought as part of a global cost-cutting programme.
Pfizer boasts three major operations centres in Ireland at Grange Castle in Dublin, Ringaskiddy in Cork and Newbridge in Kildare.
Its Ringaskiddy operation - which dates back to 1969 - was one of the firm's largest manufacturing centres outside of its US base.
The original decision by Pfizer to locate in the Cork harbour town helped it emerge as one of the leading pharmaceutical manufacturing centres in the world.
Sildenafil, the key ingredient in Viagra, was manufactured at the Pfizer facility in Ringaskiddy.
Trade unions are now to seek clarification on the precise plans involved.
All the job losses are expected to be achieved on a voluntary basis.
Negotiations will now take place over the packages to be offered to the workers involved.
Business leaders and politicians in Dublin, Cork and Kildare expressed concern at the announcement with Pfizer ranked as one of Ireland's 'blue chip' employers.
In a statement, the company said that it was proposing a reduction in manufacturing personnel following the detailed operational review but was trying to minimise the number of jobs involved.
"Pfizer recently launched a multi-year, multi-phased programme designed to assess the efficiency of our manufacturing focused on finding operational efficiencies to increase productivity within the network," a spokesperson said.
"As part of this process, we have conducted a series of evaluations and have proposed a reduction in the number of people supporting our overall manufacturing operations in Ireland."
"These proposals impact colleagues across the Grange Castle, Ringaskiddy and Newbridge sites during the last quarter of 2024 and into 2025."
"Reducing jobs is always the very last resort and we have been doing all we can to reduce costs elsewhere and minimize the impact on our people."
"We are actively engaging with colleagues and their representatives, and all job-related decisions will be made with transparency, respect, and in compliance with all applicable laws."
"For over 55 years, our sites in Ireland have played a key role in the global network, manufacturing many of our leading and newest medicines."
"We have invested $9 billion since operations began in 1969 and continue to expand with construction underway for our $1.3 billion investment into Grange Castle, projected to create a substantial number of new roles at the site by 2027."
