"Woke up filled with hope. Dreams come true y'all... thank you @xtina. I love you so much," Lovato said alongside a photo of "Fall in Line" being nominated for Best Pop Duo/Group Performance.
"Fall in Line" was released in May and appeared on Aguilera's eighth studio album Liberation. A music video was also released that featured the singers escaping from a hi-tech prison.
The Grammy Awards will be presented on Feb. 10 at the Staples Center in Los Angeles. The event will be broadcast on CBS.
Lovato made headlines recently when she uploaded a photo of herself practicing Brazilian jiu jitsu following a stint in rehab. Lovato returned from rehab in November after her highly-publicized overdose in July.