The 19-year-old, who hasn't played for the Reds since our clash with Leicester on 7 February, looked fit and fresh in advance of our trip to France.
Ruben Amorim watched on from a distance for the open session at our base.
It remains to be seen whether or not Mainoo will be involved against Lyon at Groupama Stadium, but the boss did provide an update following the 1-1 draw with Manchester City at the weekend.
"Kobbie Mainoo is training with us, we want to be careful, again, with our players, but maybe he’s going to be in our squad," said Amorim.