Johann Hahlen was born in Trier on 13 December 1942.
After achieving his university entrance qualification, Johann Hahlen studied law in Freiburg from 1961 to 1965.
This was followed by basic military service from 1966 to 1967, legal preparatory service from 1967 to 1970, and the second state examination in law in Stuttgart in June 1970.
From 1970 to 1972, Johann Hahlen worked as an employed lawyer in Cologne. In April 1972, he joined the Federal Ministry of the Interior, where he worked in various functions and departments: as Assistant Head of Section in the departments of public service, constitution, constitutional law and administration, external probationary period at the Federal Office of Administration, Department of sports and media, Section for the borders commission, transit commission, and Berlin affairs, Department for police affairs.
From 1983 to 1988 he worked for the working group on domestic affairs of the CDU/CSU Bundestag parliamentary group. During that time, he was on leave from the Federal Ministry of the Interior.
From 1988 to 1992, he was Head of the budget Section of the Federal Ministry of the Interior, and from 1992 to 1995 Head of the Sub-Directorate for constitutional law at the Federal Ministry of the Interior.
From 2 October 1995 to 5 October 2006, Johann Hahlen was President of the Federal Statistical Office and until 18 January 2007 Federal Returning Officer.
Beside the first Federal Returning Officer Dr. Dr. h.c. Gerhard Fürst, the seventh Federal Returning Officer Johann Hahlen was the only one to perform that function for more than eleven years. With three Bundestag elections (27 September 1998, 22 September 2002 and 18 September 2005) and two elections to the European Parliament (13 June 1999 and 13 June 2004), Mr. Hahlen was responsible for conducting the largest number of all-German elections.
After the Bundestag elections of 1983 and 1972, the Bundestag election held on 18 September 2005 was the third early Bundestag election since the founding of the Federal Republic of Germany.
