Tigers vice-captain Allen and Tonga international forward Mafi are included in the 23 for the vital Heineken Cup Pool 5 fixture against Benetton Treviso in Italy.
Allen has made only four appearances this season after suffering a freak leg injury in the home game against Northampton Saints in October – on the day he collected his Tigers cap in recognition of 100 starts since his arrival at Welford Road in 2009 - which required surgery.
Mafi, meanwhile, returns from compassionate leave after starting just one game so far this season.
“Anth was down to be in the 23 last week but in the end he didn’t feel quite right and we decided to take him out and give him more time,” said Tigers director of rugby Cockerill.
“He has trained and has come through well enough to be involved.
"Player welfare is key. In the short term we would have liked him to be involved last week but you have to do the right thing, certainly with a serious injury like he had.
“He is a very good player, a very good athlete and he has worked very hard with the medical staff to get back from a serious injury.”
Mafi, who last featured in a matchday squad in the game against Harlequins at the beginning of November, is also ready to resume his place in the Tigers squad.
“Steve arrived at the weekend and went straight back into training with us this week. It’s good to have him back and it is important to have him back in the mix,” added Cockerill.
Dan Bowden has had surgery on his fractured cheekbone and could be out for 8-12 weeks. He joins Manu Tuilagi, Geoff Parling and Tom Croft on the long-term injured list.