Meanwhile, husband Eddie Cibrian donned a fake beard and served up a little Kenny Rogers, which was only appropriate seeing how Rogers and Parton famously collaborated on the 1983 hit "Islands in the Stream."
"It's all coming together! This hair & makeup is taking a while. God bless her!!!!!" she wrote.
Rimes later shared, "Happy Halloween and may you all find your 'Islands in the Stream' #Halloween."
The sight of the couple enjoying the holiday comes amid claims by Star magazine this week that the two are on the outs.
"Completely untrue," a rep for Cibrian told E! News. "Amazing how Star dreams up these stories and then prints lies as possible truth."