Because his successor-elect, Governing Mayor of Berlin Otto Suhr, had died on 30 August 1957, Sieveking was re-elected as President of the Bundesrat in order to avoid a vacancy.

He resigned on 1 November 1957, when Willy Brandt became the new Governing Mayor of Berlin and President of the Bundesrat subsequently.

Because of that, Sieveking is, as yet, the only President of the Bundesrat to be re-elected to a second consecutive term (seven other persons have held two non-consecutive one-year-terms).

Many streets and places in Hamburg were named after them: e.g. Sievekingsallee, Sievekingdamm or Sievekingsplatz (53°33'19"N 9°58'34"E).

He won the election, in his office term he reformed the school system and initiated the town twinning with Saint Petersburg (then Leningrad) in 1957.