The 37-year-old actress has reportedly been ''having fun'' with the former 'Saturday Night Live' comedian for a couple of months.
An insider close to the 'Mad Men' beauty told Us Weekly magazine: ''It's very new. They're seeing where things go. He's a good guy.''
The couple met on the set of their new TV series, and January admits she loved working with Will, 44.
She said: ''I'm a huge fan of Will. I got to go to work and laugh my ass off.''
The actress, who has three-year-old son Xander and has never revealed his father's identity, split from director Noah Miller in early 2013 and later insisted she was happily single.
She said at the time: ''I don't have room for anything else, so I don't know how I would have done it with a partner.
''I knew I would be raising my son alone.
''It was something I went in to knowingly, I was prepared mentally - and I was excited about it.''
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