The Scottish Premiership champions confirmed the signing of the Switzerland international from Premier League side West Ham last week.
Having signed a four-year deal with the Glasgow club, Ajeti could be in line to make his debut for Celtic when they face Icelandic side KR Reykjavik in the first qualifying round of the Champions League on Tuesday.
Speaking ahead of the game, Celtic manager Lennon has revealed that the 23-year-old will be in the squad, but admitted that the striker is not ready to start yet.
However, the Northern Irishman has tipped Ajeti to make an impact at Parkhead, labelling him a 'natural goalscorer'.
"He'll be in the squad tomorrow but he's not ready to start as he's got a little more work to do", Lennon told a press conference.
"He'll be a good signing for us.
"He's a natural goalscorer and that was a position we were looking to strengthen."
Ajeti will be looking to revive his career at Celtic Park, having failed to score in his only season in the Premier League last term.
