Concern Worldwide (often referred to as Concern) is Ireland's largest aid and humanitarian agency. Since its foundation 50 years ago it has worked in 50 countries. According to its latest annual report, Concern helped 28.6 million of the world's poorest and most vulnerable people in 2019, while responding to 82 emergencies in 24 countries. Concern aims to help those living in the world's poorest countries. Concern is engaged in long-term development work, in addition to emergency relief in Africa, Asia and the Caribbean. Concern's core work focuses on health, hunger and humanitarian response in emergencies. The charity works in partnership with small community groups as well as governments and large global organisations. Concern is one of fourteen fully certified members of Humanitarian Accountability Partnership. It has no religious or political affiliations.

Concern Worldwide US is an affiliate of Concern Worldwide. It has offices in New York City and Chicago. Concern Worldwide is a partner of One Campaign.

Concern Worldwide UK is a UK charity that supports the overseas work of Concern Worldwide. It is a registered charity in the UK (number 1092236 England and Wales and SC038107 Scotland). Danny Harvey became executive director of Concern Worldwide UK in late 2019.