Emotions were high when Jai Arrow led the Rabbitohs out at Robina on Saturday.
Arrow, who was diagnosed with motor neurone disease (MND) earlier this year, was named captain and in the No.23 jersey for his 99th match for the club.
His team lifted after he was substituted off immediately, leading 28-0 before withstanding a Titans comeback.
Mitchell came on in the 50th minute for his first match since round 11, after recovering from back and calf injuries.
He was put on report for a high shot on Gold Coast fullback Keano Kini before handling twice to set up a crucial try for centre Tallis Duncan.
The win took the Rabbitohs to sixth on the ladder and four points clear of ninth with one round remaining.
The 31-year-old Arrow had earlier been granted permission by the NRL to count his appearance in the record books.
As the beautiful notes of "You'll Never Walk Alone" played loud, Arrow took his place under the goalposts at the northern end of the stadium to rapturous applause.
He waved to the crowd, thumped the crest laden with magnificent history on his chest and was proudly interchanged for lock Cameron Murray, before taking his place on the bench.
It was fitting that Murray scored the first try under the sticks with a rampage that Arrow has made so many times in his stellar career.
Before the match began, coach Wayne Bennett assisted Arrow to put on his socks and boots in a touching dressing room moment.
The coach was proud of how his players handled a "great occasion" full of emotion.
"It was a great day," Bennett said.
"I never thought my players wouldn't be emotional about it, but they had to handle those emotions. They had a job to do and they did it great. I couldn't be more proud of them."
Arrow will reach his 100-game milestone with the Rabbitohs next week against the Sydney Roosters.
The Titans wore a tribute jersey with Arrow's image on the front for their dedicated "Stand with Jai" round. Arrow, a Burleigh Bears junior from just down the road, played 56 NRL matches for the club.
South Sydney were unstoppable early with Murray on fire. After scoring, he put Keaon Koloamatangi over then carved through to send Euan Aitken in.
David Fifita, against his old club, swatted five Titans away to race 75m and score before Murray bullocked over again to make it 28-0 after 27 minutes.
The visitors took their foot off the pedal and Gold Coast scored either side of halftime through captain Tino Fa'asuamaleaui and hooker Oliver Pascoe.
Winger Siale Faeamani scored after a Lachlan Ilias bomb in the 54th minute to send shivers through the Souths camp.
Mitchell came on and got himself in early trouble with his high shot before turning provider for Duncan, who scored his second try late in the match to put the result beyond doubt.
Try-scoring whiz Alex Johnston iced the win to give Arrow an afternoon in the sun to remember.
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