Mr Young received 2,920 first-preference votes, Conservative candidate Eleanor Price got 1,420 and Labour’s Margaret Graham 1,205, but when second preferences were counted the transfers pushed Labour into second place.
The turnout for the by-election, held on Thursday, was 31.6 per cent, which is seen as around average for council elections.
Celebrating his victory, Mr Young said: “It feels good to have had the confidence of the people of Craigentinny/Duddingston. We worked hard for all the votes."
And he said he wanted to work across parties with the other councillors for the ward in the interests of the community. “I would never call myself a politician – I’m much more about collaboration and working together to achieve what people in our area need.”
The by-election was caused by the resignatioon on health grounds of SNP councillor Ian Campbell who was elected in 2016.
Mr Young works as civic participation manager for a disabled people's organisation and previously worked in finance then community development, spending time with Voluntary Service Overseas in India and at the Corrymeela peace and reconciliation centre in Northern Ireland.
A total of seven candidates stood in the by-election.
John McLellan, Conservative councillor for the ward, said national factors had affected the vote. "Despite a strong campaign to get a message out about the council, it appears that was trumped by the national picture.”
Labour agent Paul Nolan hailed the result as a good one for his party. “We’re very happy with it. We hit the crossbar but next time the ball will be in the net.”
The Greens increased their share of the vote from 11.7 per cent to 15.8 per cent and came just 20 votes behind Labour in first preferences. Candidate Ben Parker said: “Having fought a forward-looking campaign about tackling the housing crisis, making our streets safe for walking and cycling and protecting green space, it's a sign that more voters than ever are tired of negative status quo politics and want to see the city move forward.”
The Lib Dems polled 631 votes, independent Andrew McDonald 93 and Scottish Libertarians 42.
Ballot papers stuck together with sellotape
Hundreds of ballot papers had to be sellotaped together at the count in the City Chambers after they tore going through the scanner machine.
Tory councillor John McLellan said: “The count was held up because the ballot papers had a little pre-stamped fold in them to make it easier to fold before you put them in the box, but as they put them through the scanners they ripped.
"They ended up having to sellotape the ballot papers together to get them properly verified. It wasn’t just a few – there were a lot. For the last part of the count there was a constant sound of tearing sellotape.”
Another source estimated “a few hundred” ballot papers were affected.
A council spokeswoman said: “A production error led to some tearing in ballot papers when they were scanned. We were still able to count these votes and the issue had a minimal impact, resulting in a very slight delay to the announcement of the final result.”