The Wrecking Ball hitmaker shared the sad news on her Twitter, writing, "My precious baby Floyd has passed away. I am broken ... I know I don't mean it but I wish he would've taken me with him. This is unbearable. What am I gonna do without him?"
Cyrus also pre-warned the audience due at her concert in Boston on Wednesday that she wouldn't be at her best, adding: "I'm sorry in advance if I am not myself ... Boston. I will try my best to be my best."
The pop star tried to keep her emotions under control during the show, but was eventually reduced to tears after telling the crowd about her heartache.
She said: "I'm sure you guys already know, but the reason I'm upset is my dog, who ... I shouldn't say he was my favourite, but he was my favourite, and he passed away. I just want to do a song for him because we used to always listen to Fleetwood Mac together and it was his favourite song."
Cyrus belted out the rock band's hit song Landslide for the crowd at the TD Garden arena, and followed the performance with tearful renditions of Lana Del Rey's Summertime Sadness and Coldplay's The Scientist.
