The Algerian international became a cult hero during his loan spell at The City Ground last season as he helped The Reds stave off the threat of the drop.
And after completing a permanent switch from Wolves during the close season, the midfielder brought more joy to the Forest faithful as his goal sank City.
He settled Forest’s nerves with a cool finish from eight yards out 19 minutes from time after excellent work by Andy Reid and new boy Simon Cox.
Reid powered to the edge of the City area before finding Cox whose first touch as a Reds player created the opportunity for Guedioura to break City’s resistance.
The City Ground erupted into life, not least in the Directors’ Box where the Club’s new majority shareholder Fawaz Al Hasawi and Chairman Omar Al Hasawi joined in the celebrations.
Boss Sean O’Driscoll gave league debuts to four of his summer signings: Danny Collins, Greg Halford, Dan Harding and Simon Gillett.
The introduction of Gillett to the starting line-up – in place of the injured Daniel Ayala – was the only change from the side O’Driscoll had sent out at Fleetwood on Monday in the Capital One Cup.
In Ayala’s absence, Greg Halford dropped into the centre of defence with Gillett operating in midfield. Latest signings Cox and Sam Hutchinson were named among the substitutes.
Forest dominated the early exchanges and Dexter Blackstock was just inches away from giving boss O’Driscoll the perfect start after just six minutes.
Radi Majewski floated over a cross from the left but Blackstock, the match-winner at Fleetwood, could only find the side-netting from an acute angle.
Majewski went close to breaking the deadlock moments later as he sent a half-volley fizzing over Tom Heaton’s bar from a partially cleared corner.
A teasing cross from Reid presented Blackstock with another opportunity in front of the City goal but the striker lost his footing at the crucial time and was unable to direct his header on target.
City, dumped out of the cup by League Two Gillingham in midweek, gave a debut to former Forest loanee Greg Cunningham, while ex-Red Paul Anderson was named as a substitute.
Cunningham was involved in a first half flashpoint with fellow Irishman Reid after play had been suspended while Guedioura received treatment for an injury.
Play should have restarted with City returning the ball to Forest, who were in possession when Guedioura went down, but instead Cunningham set off on a mazy run towards the home side’s goal before being upended.
Reid reacted angrily and after both players squared up to each other, referee Nigel Miller had no alternative but to show the pair of them yellow cards.
City had appeals for a penalty waved away just seconds before half-time as Liam Fontaine was sent tumbling in the area by Collins, who appeared to handle the ball in the process.
And the visitors went close to breaking the deadlock at the start of the second half as Fontaine glanced a header from a Cunningham free-kick just inches wide of Lee Camp’s right-hand upright.
Brendan Moloney, who kept his place at right back despite the arrival of Hutchinson from Chelsea, blasted a long-range shot narrowly wide as The Reds strived for an opening goal.
Forest introduced new boy Cox to the action midway through the second half and he made an immediate impact as he played a part in the build to Guedioura’s goal.
Cox, who had completed his move from West Brom earlier in the week, and Blackstock went close to adding to Forest’s lead.
And although they survived a scare when substitute Anderson’s pull back flashed across the face of Camp’s goal, it was a case of mission accomplished for O’Driscoll and his players on opening weekend.
Forest: Camp, Moloney, Halford, Collins (c), Harding, Gillett, McGugan (Cox 68'), Guedioura, Majewski (Lascelles 90'), Reid (Greening 90'), Blackstock.
Subs not used: Evtimov (GK), Hutchinson, McGoldrick, Tudgay.
Scorer: Guedioura 71'
Bristol City: Heaton, Woolford (Anderson 78'), Adomah, Cunningham, Foster (Elliott 70'), Pearson (Pitman 89'), Mark Wilson, Stead, Fontaine (c), Carey, Skuse.
Subs not used: Gerken (GK), James Wilson, Kilkenny, Morris.
Bookings: Cunningham 38'
Attendance: 21,575 (Away: 1,201)
Referee: N. Miller