A gambling granny left her 5-year-old granddaughter in her car while she ducked into a Queens casino, cops said.

Renee Osby, 56, allegedly went into the World Resort Casino on Rockaway Boulevard near Aqueduct Road around 11 a.m. Saturday, authorities said.

She left the child in her 2004 red Cadillac Escalade for over an hour, sources said.

The girl was spotted by a security guard, who dialed 911, sources said.

Police arrested Osby, a home health aide from Brooklyn, cops said.

She was charged with acting in a manner injurious to a child, cops said.