Lasse Dahl Jensen is the second child of Robert Jensen and Ulla Dahl. He was born 1 March 1997. He has older sister Anna Dahl-Vestergaard from 1995, younger brothers Johan from 1999 and Jacob from 1999, and younger sister Laura from 2000. He is the father of Anton Dahl, and the boyfriend of Sara Skov. He lives in Skovlunde, Ballerup, Denmark.
In 2000, when he was 3, he started nursery at Børnehuset Ved Skoven, in Egebjerg Ballerup, Denmark. In 2003, when he was 6, he started 0th grade at Egebjergskolen, Ballerup.
In 2013, when he was 16, he started high school, stx, at Borupgaard Gymnasium in Ballerup, where he took Danish, English, History and Biology at level A. In 2016, he graduated with a GPA of 10.2. In August 2017, he will begin a bachelor degree at Copenhagen Business School.