Hamilton police said at around 11 p.m. someone launched the brick at the home on Beechwood Avenue. The brick landed beside the baby's playpen and glass shards from the window hit the infant.
The child was taken to hospital and treated for minor injuries, but has since been released.
Following an investigation, city police say there was a neighbourhood feud between two families in the John Street North and Murray Street East area.
In a media release, Hamilton Police added, "A resident on Beechwood Avenue had his window broken earlier and suspected that it was done by someone living at the victim's home. In response, the suspect attended the address and threw a brick through the window."
A 17-year-old male has been arrested for mischief endangering life and has been held for bail.