Henn started his career with Hindu Club in Argentina. In 2005, he was signed by the top French club Stade Francais who compete in the Top 14. After one season, in 2006, he joined US Montauban who play in the Pro D2, the second level of domestic competition in France. He returned to the Top 14 when he was signed by CA Brive. After four seasons, he left Brive and he signed for Limgoes for the 2013-14 season, competing in Federale 1, the third level of domestic competition in France. On 10 July 2014, Henn was signed to the English club London Welsh who compete in the Aviva Premiership from the 2014-15 season.