Parents can now apply for additional unpaid leave from work following the introduction of new parental leave legislation due to take effect in September.
An amendment to the Parental Leave Act will see parents get an extra four weeks unpaid leave, on top of the current 18 weeks entitlement until a child reaches their eighth birthday.
Next year, the entitlement will go up from 22 weeks to 26 weeks.
The legislation was initiated by the Social Democrats with cross-party support.
The party's co-leader Róisín Shortall said the move could potentially affect half a million working parents.
"It's very badly needed. Ireland ranks very poorly in European terms for parental leave and flexible work options," Ms Shortall said.
She also welcomed the support from other parties and said it was a good example of "new politics".
In addition, the qualifying age of the child goes from eight up to 12.
Parents have to give six weeks notice to their employer before the leave is due to commence.
IBEC said employers were broadly supportive of the initiative and added it enhances workplace diversity and allows employers to retain talent.
Rhona Murphy, Head of Employment Law Services with IBEC, said: "Some employers, depending on their scale and the demographic of their particular employees, may not be impacted that much at all.
But our concern is for smaller employers they may face some real challenges just because of how the legislation is structured."
"In particular the new ability to take the leave in smaller blocks of one week can make it difficult in some circumstances for employers to recruit replacements.
That can create a difficulty for colleagues who are remaining in the workforce," Ms Murphy added.
Both parents have their own equal, separate entitlement to parental leave.
David Stanton, Minister of State at the Department of Justice, said the government was pleased to work with Oireachtas members to enact the legislation.
Mr Stanton also said that later this year a new social insurance-based parental leave system will be available to parents providing two weeks of paid leave to both parents during the first year of a child's life.
An estimated 60,000 parents a year are expected to gain from this change.
"This is in addition to the two weeks paid Paternity Leave for fathers which commenced in 2016 and which almost 70,000 fathers have applied to the scheme since its introduction.
The Government will continue to support parents by providing greater flexibility in achieving and managing a work life balance", Mr Stanton said.