As a young man Henri became interested in politics and was Mayor of Proven from 1960 to 1970 and of the newly merged municipality of Proven-Krombeke from 1971 to 1976. Almost 20 years later in 1995 he became Mayor of Poperinge, of which Proven had been a part since the large scale-merger of municipalities in 1976. Count Henri d'Udekem d'Acoz was active in the legal profession for over 50 years. His career included a spell as Solicitor General at the court in the West Flemish town of Ieper.
He shot to national (and international) fame in 1999 when it was he that announced the engagement of his niece Mathilde with the then Crown Prince Filip.
Between 1999 and 2009 Henri d'Udekem d'Acoz and his two brothers fought each other in a bitter inheritance battle. Insults and accusations were thrown. Things escalated when his brother Patrick bought one of his his daughter a farm next to the family estate in Proven. Henri, who was then Mayor of Poperinge had the building declared uninhabitable.
Patrick accused his brother of conflict of interest, saying that he was using the farm to get at him. The case came before the criminal court in 2005 and Henri d'Udekem d'Acoz was fined 4,900 euro. It was until a year after Patrick d'Udekem d'Acoz’s death in 2009 that the feud came to an end.
Then aged 71 Henri d'Udekem d'Acoz married Marie-Madeleine Kervyn d'Oud Mooregehm in 2005. In 2010 he hit the headlines again after the Flemish Christian democrats threw him out of the party for allegedly having joined the Flemish nationalist party N-VA.
However, N-VA said that while the Count had been sent a membership form and an information brochure he was not (yet) a paid-up member of the party.
At the end of 2010 there was more controversy when he was accused of not maintaining the neo-classical 't Couthof Castle in which he grew up. He eventually gave the castle to Bernhard d'Udekem d'Acoz, his brother Raoul’s oldest son.
In 2015 Henri d'Udekem d'Acoz was found guilty of deception and given a 6-month suspended prison sentence and issued with a fine. He always maintained his innocence and was later acquitted by the Court of Appeal.