From the summer of 2000 until December 2004 Rahmen was
coach of
SC Dornach in the
1. Liga, first as player-coach then as head-coach. Then he was hired by FC Basel to coach their U-18 youth team. In 2007, he took over as coach of the U-21 team. In October 2011, as the that time Basel first team manager
Thorsten Fink left the club and signed a contract to become manager of
Hamburger SV in the
Fußball-Bundesliga, Rahmen followed him and became his
assistant. As of 1 July 2018, was appointed as the head coach of
FC Aarau and had signed a two-year contract. As the contract expired it was not extended. On 21 September 2020,
FC Basel announced that they had hired Rahmen as second assistant trainer under their new manager
Ciriaco Sforza. On 6 April 2021, the club announced that, due to the lack of sporting success, FC Basel 1893 were separating themselves from head coach
Ciriaco Sforza with immediate effect. They also announced that they had separated themselves from assistant manager
Daniel Hasler at the same time. Until the end of the season, the first team would be looked after by the other previous assistant Rahmen, on an interim, basis as head coach. In the communique on the following day it was announced that Ognjen Zaric was appointed as assistant manager. Zaric had been coach of the Basel 1893 U-18 team since summer 2020 and before that he had been head coach of
TSV 1860 Rosenheim in the
Regionalliga Bayern, the fourth tier of German football. On 20 May 2021,
FC Basel announced that Rahmen had signed a new contract that made him head coach of the FCB first team. To the end of the calendar year there was an amount of press reports that Rahmen would be replaced, but then, on 31 December the club announced that the contract with head coach had been extended for a further year until summer 2023. However, just a few weeks later, on 21 February the club announced that the contract with Rahmen had been terminated, due to "unsatisfactory sportive development of the team and lack of clear perspective". Between 2022 and 2023, he was the coach of the
Switzerland national under-21 football team. On 14 June 2023, he was appointed head coach of
FC Winterthur. He will join the club following the
2023 U21 Euros. With Winterthur he managed to qualify for the Championship Group during the regular season, despite coaching one of the weaker teams of the league on paper. On 14 May 2024, he was announced as the new head coach of Swiss serial champions
BSC Young Boys for the upcoming season. Following a poor start in the league, which saw the team in last place with just six points and one win after nine games played, his appointment with Young Boys was terminated. Despite the poor league results, he did successfully qualify to the
group stage of the
UEFA Champions League, beating
Galatasaray 4–2 on aggregate in the
playoff round of qualifying. However, at the time of his dismissal, Young Boys sat bottom of the Champions League table, following 0–3 and 0–5 losses to
Aston Villa and
FC Barcelona, respectively. On 22 October 2025, he returned to
FC Winterthur, replacing recently dismissed
Uli Forte and taking over the team sitting in last place with just two points out of nine games in the
2025–26 Swiss Super League. ==Personal life==