The SPL Champions will line up in Group G with the Spanish giants alongside Benfica and Spartak Moscow.
"It's very exciting to be in a group with Barcelona," said Lennon.
"It's a tough, tough group. All the teams play good football, so it should be quite attractive to watch.
"We're familiar with all three teams. Under Gordon [Strachan] we played Barcelona and Benfica, and we also knocked out Moscow in a playoff."
Celtic overcame Swedish side Helsingborg to reach the group stages.