Nagelsmann joined the 1899 Hoffenheim youth academy in 2010 and coached numerous youth teams in the following years. He was an assistant coach during Hoffenheim's 2012–13 season, and up until 11 February 2016, was coaching the club's U19 team. He coached Hoffenheim's U19 "junior team" to win the 2013–14 Under 19 Bundesliga title. During his time as assistant coach, goalkeeper Tim Wiese referred to Nagelsmann as "Mini-Mourinho."