Emma Noblet, from Ingol, and other residents were shocked when they saw a post from the youngster’s mum on social media.
The youngster had been delivering in the Conway drive area when the thief struck.
He would have had to do his round on foot every day if locals had not stepped in.
Emma set up a crowdfunding campaign to raise cash for a new bike for him, and within hours, people across the city had donated £343 - enough for a new bike and a security lock.
She said: “ I had just come across the post while scrolling on my news feed and I felt for him. He gets up 7 days a week to do his job and to make some money for himself, and I thought how unfair.
“I have a good network of friends so I knew I could raise some funds towards a new bike. I have three boys myself and it was a good lesson for them too.
"I just wanted him to know that there are people out there who wanted to help him.. I didn’t want one person’s actions to dampen his day instead now, he knows that there are good people willing to help.”