The culprits spray-painted part of the playground's sign reading "Ana Grace: Love Wins" with what appeared to be the letters "BEKS," a peace sign, the number 2 and the words "Sandy Hook."
Deputy Chief Brian J. Foley, of the Hartford Police Department, said officials would "rectify" the sign, describing the act as "senseless."
A family friend told WFSB that she removed the graffiti on Sunday night.
Ana Grace's playground is part of a project called The Sandy Ground Project, which is building 26 area playgrounds in honor of the children and educators who died at Sandy Hook Elementary School in December 2012.
The playground is purple, Ana Grace's favorite color.