"Cath and Sam are giving it another go," a source revealed to the Mirror. "They had a relationship break but still continued to train together and this has brought them back together again.
"They've officially been seeing each other for a couple of weeks. They had a discussion about what they both want and have come to the conclusion they want to be together."
The source added that the pair, who split back in March, are taking things slowly this time around and don't want to spoil the rekindled romance by going public just yet.
According to reports, the couple mutually decided to call time on their romance earlier this year after realising they wanted "different things" from the relationship.
Catherine, 29, had spoken of her desire to have a "big family" and it's thought that may have contributed to her split from Sam, 22.
"They have just grown apart. The age gap was an issue because they want different things," a source told the Mirror. "Cath is at a stage where she wants to settle down and Sam is still only 22 so he isn't ready for that sort of commitment.
"It was a mutual decision to call it a day. They will remain friends and plan to continue training with each other, though that is going to be difficult, especially when the split is still raw and causing pain."
Catherine and Sam started dating early last year, and their love of fitness led them to create their own website SamandCath.com, offering tips on training and diet. A matching Twitter account, which the couple used to tweet messages of love to each other, has since been taken down.
They had recently also started up their own firm, Dream Partners Limited, with plans to bring out a DVD and exercise book.
Catherine, who has played Eva Green on Corrie since 2011, has slimmed down from a size 22 to her current svelte size 10 figure in the past 10 years - and frequently credited Sam with helping her stay in shape .
After their split, Catherine said she was happy being single. "I'm so happy at the minute," she said. "Sam and I are still great friends. It just didn't work out, but I'm fine.
"I'm cracking on with work and if I meet someone new then great."