Cork South West and Fine Gael TD Jim Daly has announced he will not contest the next general election and is to leave politics to spend more time with his family.
Mr Daly said in a video message that the decision was very difficult for him.
He has served as Minister of State for Mental Health and Older People for the past two years.
Deputy Daly said he has found it increasingly difficult to balance political life as a career politician with family life.
He lives in Clonakilty and said that spending three to five days a week in Dublin in his ministerial role had become unworkable.
Mr Daly has represented his west Cork constituency for 16 years.
He said he was proud of his record of delivery in infrastructure, on flood schemes, schools, roads and hospitals and in particular achievements made during his time at the Department of Health.
He said that he has learned that you cannot change the world, but that one of the greatest honours of his life has been to change someone's world during his political career.
Mr Daly thanked all his supporters and said it has been an extraordinary honour to fight several elections successfully and be a poll topper.
Thank you from the bottom of my heart to all my friends and supporters in West Cork. It has been an honour.— Jim Daly (@jimdalytd) September 20, 2019
I will continue to carry out my duties on your behalf until the next general election. pic.twitter.com/KLOt0aKPKg
Speaking on RTÉ's Today with Sean O'Rourke, Mr Daly said he does not anticipate stepping down from his junior ministry ahead of the next general election, but it is ultimately a matter for the Taoiseach to decide on.
He said his eldest son was just two weeks old when he went into politics and his family have been second to politics for the last 16 years and he now wants them to come first.
Minister Daly said that he informed the Taoisach this week who supported him and appreciated his decision.
In a statement, Leo Varadkar said Mr Daly has done a "stellar job" and has "always admired his directness, his capacity for independent thought and his unique way of doing things.
"He has secured massive resources for mental health, with the Budget for that area now approaching €1 billion per annum.
"He is also pressing on with plans to make the Fair Deal scheme fairer for farmers and business people, and a new transformative statutory scheme for home care."
Mr Varadkar said Fine Gael was the strongest party in Cork South West in the last election and Senator Tim Lombard has been selected as the candidate for the constituency.