The 23-year-old singer didn't say if she knew the baby, or had just been sent the video, but simply captioned it with heart emojis.
The video starts off with the baby's lip quivering, before she starts sobbing as Grande sings the chorus.
In between sobs, the baby starts to try and sing herself while Grande is hitting the high notes.
We can totally relate to the tears.
"Awww omg," one person commented on the video. "Baby felt your heart! So did I."
Another wrote: "Watching this just set me off again, that performance had me in tears."
For those of you who missed it, watch a clip from Grande's performance below.
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