Making his appearance from the bench against Harlequins on Friday evening, Parling twisted his knee after his studs became caught in the turf.
"It's a crying shame for us and for him," Tigers director of rugby Richard Cockerill told BBC Radio Leicester.
"It's horrendous for him first and foremost - and really bad news for us because we thought we were getting him back and he would really bolster our second row and forward options. It is a massive loss.
"We have to get him fit and well and the club have a very good track record for looking after players really well."
The England international powerhouse, who was named in the Tigers' original European squad will undergo surgery in the coming days and will miss the rest of his side's Heineken Cup adventure.
Leicester currently lead Pool 5 of the competition and face back-to-back games against Perpignan in rounds 3 and 4 in December.