Head coach Nigel Davies has chosen to bring back the influential and experienced outside half a week before the Scarlets' opening European cup game against Brive at Parc y Scarlets on October 10th.
Jones was rested as a precaution at last weekend's high profile Welsh derby last weekend in Cardiff, to recover from a slight ankle injury.
Davies said: "Stephen will play for us on Friday which will give him an opportunity to roll into the European game. He's massive for us - he has that level of experience and mental toughness on the field that we need for this game. He brings a real composure and understanding to the team and does boss games particularly well."
"It's not only what he does on the field, it is what he contributes off the field as well and he is hugely respected by all the guys."
On preparations for Ulster, the Scarlets head coach said: "It's a short turnaround for us, however we are comfortable, we know where we are and what we want to do. We are going to have to be that much better than them to win up there and be on top form to get a result; but in any case that's where we need to be now going into Europe."
The Scarlets will rest captain Mark Jones, who picked up a dead leg against the Blues, as well as player-coach Simon Easterby, who left the field after aggravating a knee problem.
Flanker Johnathan Edwards makes his first start of the season ahead of Richie Pugh at openside, a reward for Edwards's impressive form at semi-pro level for Llandovery.
Wales prop Rhys Thomas will also return to the side having missed the last two matches with stitches in a cut knee.
Captain Mark Jones said Friday's encounter will be about registering much needed points in the league and said his Wales team mate's return would boost the team: "I think the team on Friday night will be bolstered by having Stephen back in the squad, he does make a big difference.
"Ulster will be in a good frame of mind leading into this game and I think it's an important game for both teams as we approach Europe. The conditions up there are often difficult and the crowds are very hostile, but these environments are one of the reasons why you play rugby and I think some of the young guys will really relish that and hopefully we can get a good victory.
"Every Magners League game is important but this game becomes important from a points point of view, and icing on the cake will be that extra bit of confidence a win will give us going into the Heineken Cup."
On the day the Wales U20 squad for the Six Nations is revealed, WRU Head of Rugby Performance Geraint John discusses the priorities of the Wales U20 programme, and moves being undertaken to make it easier for Welsh Exiles to be part of the WRU pathway - and to help keep Welsh qualified players in Wales
It was a double celebration for Wales and Ospreys scrum-half Rhys Webb when he called at the home of Welsh rugby to help commemorate the first anniversary of Principality Stadium and his return to fitness this weekend ahead of the RBS 6 Nations.
Prior to their departure to Wellington for the next leg of the World Series, Wales trained with England and Ireland. WRU TV caught up with Owen Jenkins who revealed the 'buzzword' which is driving the Wales squad on.
Wales head coach Rob Howley explains his decision to change the captaincy of the national side with Ospreys second row Alun Wyn Jones taking over from Sam Warburton for the forthcoming RBS 6 Nations. Howley is hoping his decision will allow Warburton to rediscover his 'mojo'.
How do you follow a dancing hippopotamus - the Ospreys wheelchair rugby team has just the 'oneness' to do it say the BBC! For a decade the sight of a herd of hippos synchronised swimming around their own private blue lagoon, has lit up our television screens at regular intervals between favourite BBC One shows. But now the nation's most watched channel has relinquished its famous amphibious mammals in favour of a new show-reel which includes the Ospreys wheelchair rugby team.
Head coach Rowland Phillips and key front rower Carys Phillips look ahead to games against Spain and Ireland as Wales Women ramp up their preparations for the forthcoming Six Nations. The two warm-up games are a 'massive opportunity to refine the squad' according to the Welsh camp.
Martyn Phillips has discussed details of the newly published 'Strategy for Welsh Rugby' which puts in black and white terms the plans and direction of the governing body of the national sport in Wales for the next decade.
WRU chief executive Martyn Phillips has urged Welsh rugby fans to follow in the footsteps of their soccer counterparts at last summer's Euro Championship by backing their team to the hilt in the upcoming RBS 6 Nations campaign.
Chief executive Martyn Phillips has highlighted the plans for Wales to become a breeding ground for national and elite club rugby coaches, which are contained in the WRU's 10-year 'Strategy for Welsh Rugby'.
Andrew Coombs is enjoying his new role as Nelson forwards coach. The former Dragons and Wales lock has big ambitions to become a professional coach but feels it's important to learn the ropes in grassroots rugby and where better than his home club Nelson, with friends and family close to hand.
Students at Brynllywarch Hall School, near Newtown, have transformed their own lives, and are now having a positive impact on others through rugby. The sport has had a life-changing effect on the well-being of the students who are now delivering rugby sessions to local primary schools and playing for a new mixed ability side
Wales reached their first semi-final since 2013 in the opening round of this season's HSBC World Rugby Sevens Series in Dubai. WRU TV's Graeme Gillespie recaps on what proved to be an eventful tournament
Wales and Ospreys back row James King, who came through the North Wales age grade system, nominated North Wales Regional Community Rugby Manager Marc Roberts, in the WRU's 'Diolch' initiative where squad players thanked those who played a part in their rise to the top.
Beating Merthyr has boosted Carmarthen Quins hopes of reaching a top eight spot in the Principality Premiership. Quins captain Haydn Pugh is delighted with his team's progress and is determined that everyone from the Under 6s through to the senior team, enjoys the ride.