Michy Batshuayi gave Valencia the lead on 26 minutes in the Group H clash, but former France striker Hoarau converted from the spot as Young Boys also scored their first goal in the competition.
The Swiss champions nearly snatched victory late on at the Stade de Suisse but Valencia goalkeeper Neto pulled off a superb save to divert Sekou Sanogo’s header onto the post.
Young Boys remain at the bottom of the group, while Valencia’s bid to qualify for the last 16 ahead of Manchester United or Juventus suffered a blow with the Spanish club on two points after three games.
Valencia, now with just eight goals in 12 matches this term, were unable to fully exploit a Young Boys defence featuring 36-year-old Champions League debutant Marco Wolfli in goal and missing the suspended Mohamed Ali Camara.
Marcelino’s side moved in front when Chelsea loanee Batshuayi gathered a pass from Carlos Soler and rounded Wolfli to slot home his second goal for Valencia.
Young Boys right-back Kevin Mbabu dragged an effort narrowly wide of the right upright minutes into the second half, with Christian Fassnacht then unable to generate enough power in his header to beat Neto.
The Swiss side’s sustained pressure paid off though as they were awarded a penalty on 55 minutes when Valencia captain Dani Parejo brought down Djibril Sow in the area.
It was the second spot-kick conceded by Parejo in three games in Europe, and after Hoarau fired the hosts level only the brilliance of Neto allowed a struggling Valencia to hold on for a draw.
The Brazilian turned behind a low strike from Fassnacht shortly after the Young Boys equaliser, but saved his best for last with a marvellous fingertip stop to deny Sanogo before he smothered the rebound at the feet of Roger Assale.