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."
The Half a Game initiative is currently sweeping across Wales and proving a major success. The scheme aims to give every young player at least half a game every weekend. WRU TV recently visited a festival in Narberth where clubs have fully embraced the initiative.
Both Bargoed and Swansea were seeking their first win of the Principality Premiership season this afternoon. It proved a fruitful day for the hosts - not only did they win, but Bargoed claimed a try bonus point.
Cardiff managed to keep their unbeaten record at home intact, but only just as Bridgend made them work extremely hard before the Blue and Blacks secured a hard fought Principality Premiership win at the BT Sport Arms Park last night.
Former Wales back row Andy Powell gives a guided tour of The Wern, home of Merthyr RFC, who are determined to prove a lot of people wrong and make their mark in their first season in the Principality Premiership.
Wales Sevens head coach Gareth Williams looks back on the Rio Sevens success where he helped GB win silver. He believes the successful campaign is a huge boost to his Welsh squad as they prepare for another World Series, as WRU TV's Graeme Gillespie discovers
British and Irish Lions head coach Warren Gatland will be heading back home to take on the All Blacks next year where for him, success for 2017 is all about going to New Zealand and winning a Test Series.
Last week all roads led to Eugene Cross Park where defending champions Ebbw Vale hosted this season's launch of the Principality Premiership. WRU TV's Graeme Gillespie was there to capture the thoughts of Damien Hudd, captain of Ebbw Vale, and WRU Head of Performance, Geraint John.
Llandovery made it three in a row when they defeated Aberavon in the final of the National Foster's 7s at BT Sport Cardiff Arms Park on Sunday. On another eventful day of sevens, Newport claimed the Plate and the Dragons won the women's crown
Last week saw Cardiff welcome players from around the world for the 21st Golden Oldies Festival. The tournament features players over 35 years of age, and this year's event saw a select few represent the WRU in a 'friendly' against the Wooden Spoon.
Wales Under 18 captain Callum Bradbury is delighted to have seen his side claim a narrow 18-17 victory against a strong SA Schools 'A' side to end the three-match Under 19 International Series in South Africa on a high note.
The Wales U18 squad spent an emotional day in the drug-riddled townnship of Hout Bay. Hout Bay Warriors President Fred Johannes said the visit was 'the talk of the town' and will dream about the day everyday for the rest of his life.
RGC 1404's new head coach Mark Jones is hoping to build 'something special' in north Wales and is already looking forward to the development region participating in the Principality Premiership for the very first time.