In a statement to Fox News on Monday, the Chief Medical Examiner Office in Connecticut said: "He died of heart disease (natural)."
Philbin's family previously confirmed to Fox News that he passed away from "natural causes." He was 88.
"We are deeply saddened to share that our beloved Regis Philbin passed away last night of natural causes, one month shy of his 89th birthday," his family announced in a statement Saturday.
"His family and friends are forever grateful for the time we got to spend with him -- for his warmth, his legendary sense of humor, and his singular ability to make every day into something worth talking about," the statement continued. "We thank his fans and admirers for their incredible support over his 60-year career and ask for privacy as we mourn his loss."
Philbin was best-known for his hosting duties on "Live!" -- with co-hosts Kathie Lee Gifford and Kelly Ripa -- and "Who Wants to Be a Millionaire."
A New York native, Regis Francis Xavier Philbin was born on Aug. 25, 1931. He was named after his father's alma mater, Manhattan's Regis High School. Philbin graduated from Cardinal Hayes High School in the Bronx before going on to Notre Dame, where he majored in sociology.
After college, Philbin joined the U.S. Navy. He then embarked on his decades-long career in television as a stagehand and a delivery boy for a station in Los Angeles, Calif. Quickly after, he became a news writer and was offered a job as a sportscaster.
Philbin went on to San Diego as a news anchor for KOGO-TV. His first shot at national exposure came a few years later as the sidekick to Joey Bishop on ABC's "The Joey Bishop Show." Philbin then moved on to KHJ-TV in Los Angeles where he hosted "That Regis Philbin Show." The show was canceled due to ratings powerhouse Johnny Carson, but it brought Philbin to the midwest for "Regis Philbin's Saturday Night in St. Louis."
After three years of commuting to St. Louis each week for a local Saturday night show, Philbin became a star in local morning television -- first in Los Angeles, then in New York. In 1985, he teamed with Kathie Lee Johnson, a year before she married former football star Frank Gifford, and the show went national in 1988.
Celebrities routinely stopped by Philbin’s eponymous syndicated morning show, but its heart was in the first 15 minutes, when he and co-host Kathie Lee Gifford -- on “Live! with Regis and Kathie Lee” from 1985 to 2000 -- or Kelly Ripa -- on “Live! with Regis and Kelly” from 2001 until his 2011 retirement -- bantered about the events of the day.
He was also the host of the prime-time game show, “Who Wants to Be a Millionaire,” briefly television’s most popular show at the turn of the century. ABC aired the family-friendly program as often as five times a week. It generated around $1 billion in revenue in its first two years -- ABC had said it was the more profitable show in TV history -- and helped make Philbin himself a millionaire many times over.
Philbin's survived by his wife, Joy, and their daughters J.J. and Joanna Philbin, as well as his daughter Amy Philbin with his first wife, Catherine Faylen, People reported.
Fox News' Melissa Roberto and The Associated Press contributed to this report