The pair are said to have spent the weekend together in O'Connell's hometown in Derby, according to The Sun.
"Tulisa likes him because he is - to use her words - a 'bit of rough'," a source told the publication.
They were photographed leaving London nightclub Aura last week.
Contostavlos had previously mentioned a new relationship on Twitter, telling her fans: "I am seeing some1!! Cus Im a bloody human being (sic).
"Like my men a bit ruff around the edges!"
O'Connell played James Cook in Skins, and has also appeared in This Is England, United and Harry Brown.
Contostavlos was rumoured to have had a fling with The Only Way is Essex star Mark Wright in Miami, but both Wright and Contostavlos have denied the reports.
The singer split from her N-Dubz bandmate Fazer back in January, reportedly after several holiday rows.
The X Factor judge will release her debut single 'We Are Young' this spring.
> Tulisa Contostavlos to write autobiography, two novels