He faces a maximum sentence of life in prison when he is sentenced.
Balfour, who was married to Hudson's sister Julia, was found guilty of three counts of first-degree murder, as well as aggravated kidnapping, home invasion, residential burglary and possession of a stolen vehicle in the shooting deaths of the Hudson sisters' mother and brother and Julia's 7-year-old son.
Deliberations by the jury of six men and six women began Wednesday evening following 11 days of testimony that included 80 witnesses and 500 pieces of evidence.
Prosecutors alleged Balfour shot his victims to death in a jealous rage because Julia had left him and was dating someone new.
Balfour's lawyers argued police wanted a quick arrest because the case was so high-profile and picked up Balfour even though there was little forensic evidence tying him to the crimes. His legal team said the Hudson sisters' brother Jason was a drug dealer with enemies who could have killed him and his relatives.