Juve appeared to be set for a routine win when Sebastian Giovinco put them ahead with a 24th minute penalty and Sampdoria had Gaetano Berardi dismissed for a second bookable offence seven minutes later.
Instead Mauro Icardi scored twice in the second half as Sampdoria hit back.
Third-placed Fiorentina also went down to a surprise home defeat, losing 2-0 to relegation-threatened Pescara, and fourth-placed Inter Milan lost 3-0 at Udinese.
Juventus, with 44 points from 19 games, still reached the halfway mark in the championship with a five-point lead over Lazio, who beat Cagliari 2-1 on Saturday. Fiorentina and Inter have 35 points. (Writing by Brian Homewood in Berne; Editing by John Mehaffey)
- Sports & Recreation
- Sebastian Giovinco