The singer/actress reunited with her producer husband on Monday, just five months after she was spotted smooching married "Smash" director Michael Morris.
McPhee, 29, and Cokas, 48, were photographed chatting and walking their three dogs together in Los Angeles. They also grabbed breakfast and coffee together at Tiago Cafe. Although the couple has been living apart for nearly a year, they have been spending time together recently.
"They are working on their marriage," a source close to the couple tells Yahoo.
The 2006 "American Idol" runner-up married Cokas in 2008.
McPhee and Cokas were separated when she was caught kissing Michael Morris in October. However, he was married to his wife of 10 years, actress Mary McCormack, at the time.
It was reported that McCormack, 45, initially kicked Morris out of the house following the scandal, although they have supposedly reconciled.
As for whether Katharine and Nick will officially get back together, that remains to be seen.