Sunday's clash will make it eight appearances and six starts this season for 22-year-old Dillane, having made his senior debut while still in the Academy last term.
Jack Carty and Kieran Marmon are retained at half back while Niyi Adeolokun, try scorer for Connacht at Parc y Scarlets last season, starts on the right wing with Matt Healy on the left.
Up front, John Muldoon, who this week signed up for his fourteenth season at the province, will captain the side. Jake Heenan, who made his season debut last week after nearly 10 months on the sidelines, will start again at openside flanker.
The bench remains unchanged with the inclusion of Muldowney.
Commenting on the team selection and the upcoming game, Pat Lam said:
"While we were disappointed with the outcome last week against Leinster, there were a lot of positives we could take from the performance. We travel with the same squad to take on a strong Scarlets side on their home pitch this weekend. There are certain aspects of our game that we are looking to improve from last week. With a solid week's training under our belt, we go with confidence knowing that if we add clinical execution to the work ethic already shown, we'll have every chance of getting the points on offer."
Connacht team to face Scarlets, Sunday, January 10th, 17:00
15 Tiernan O'Halloran
14 Niyi Adeolokun
13 Bundee Aki
12 Craig Ronaldson
11 Matt Healy
10 Jack Carty
9 Kieran Marmion
1 Finlay Bealham
2 Tom McCartney
3 Nathan White
4 Ultan Dillane
5 Andrew Browne
6 John Muldoon (captain)
7 Jake Heenan
8 Eoghan Masterson
Replacements:
16 Dave Heffernan
17 Ronan Loughney
18 Rodney Ah You
19 Aly Muldowney
20 Sean O'Brien
21 Ian Porter
22 AJ MacGinty
23 Rory Parata
Unavailable / Injured: Denis Buckley, JP Cooney, Ben Marshall, Quinn Roux, Nepia Fox-Matamua, Eoin McKeon, John Cooney, Dave McSharry, Robbie Henshaw, Conor Finn, Darragh Leader.
Scarlets v Connacht
Sunday January 10th
Parc y Scarlets
Kick off 2:30pm
Live on S4C / TG4
Referee: Marius Mitrea