The Samoan international winger replaces Andy Forsyth in the Tigers backline, while Sam Harrison makes his first Aviva Premiership start of the season at scrum-half.
In the forwards, Julian White returns at tighthead prop after missing the last two games and Geoff Parling continues in the second row after making his comeback from injury last weekend.
Commenting on the return of his first World Cup players, Tigers director of rugby Richard Cockerill said: “It’s great to see Alesana Tuilagi and Martin Castrogiovanni back at the club this week.
“Castro has returned with a slight hamstring injury but with Julian White back to fitness we want to give him time to recover fully. Alesana enjoyed probably his best-ever season with us last year so it is great to have him back and in the team.
“It is important for us to have those world-class players back in the squad and it is important for the supporters too.
“We’ve had a tough start and Quins have been going very well, but we’ll battle on and we’ll certainly be up for it on home soil at Welford Road.”
Match tickets are available now from the Tigers ticket office. Phone the hotline on 0844 856 1880, call in at Welford Road (open until 5pnm Friday and from 9am Saturday) or book online and collect on the way to the game.
Leicester Tigers (v Harlequins, Welford Road, Saturday 4.45pm)
15 Niall Morris
14 Mathew Tait
13 Matt Smith
12 Billy Twelvetrees
11 Alesana Tuilagi
10 Jeremy Staunton
9 Sam Harrison
1 Boris Stankovich
2 George Chuter (c)
3 Julian White
4 Ed Slater
5 Geoff Parling
6 Steve Mafi
7 Ben Woods
8 Julian Salvi
Replacements
16 Tom Youngs
17 Michael Holford
18 Peter Bucknall
19 Graham Kitchener
20 Ben Pienaar
21 James Grindal
22 Scott Hamilton
23 George Ford
Harlequins
15 Mike Brown
14 Seb Stegmann
13 George Lowe
12 Jordan Turner-Hall
11 Sam Smith
10 Nick Evans
9 Karl Dickson
1 Joe Marler
2 Chris Brooker
3 Tim Fairbrother
4 Ollie Kohn
5 George Robson
6 Chris Robshaw (c)
7 Luke Wallace
8 Chris York
Replacements
16 Joe Gray
17 Mark Lambert
18 James Johnston
19 Charlie Matthews
20 Will Skinner
21 Richard Bolt
22 Rory Clegg
23 Tom Casson
