DeMentri graduated from Temple University with a B.A. in broadcast journalism. He also was a member of the Temple Owls football team from 1983 through 1986, where he played the position of linebacker. DeMentri is also an alumnus of Pennsylvania's famous "Big 33" High School Football All-Star Game. He began his broadcast journalism career as a Sports Producer for WPVI-TV in Philadelphia and worked for WOI-TV as a Weekend Anchor in 1989. He was later an Investigative Reporter and Anchor for WDIV-TV in Detroit, Michigan, WPRI-TV in Providence, Rhode Island and WICS-TV in Springfield, Illinois.
In 1993 DeMentri joined CBS' flagship WCBS-TV in New York as a reporter, and became anchor of the station's weekend evening newscasts. He stayed there until 2003, when he moved to NBC's Philadelphia affiliate, WCAU-TV. DeMentri won several awards for his reporting for WCBS and WCAU, including seven Emmys for investigative reporting and a National Edward R. Murrow Award for his reporting on the September 11, 2001 attacks on the World Trade Center. While at WCAU DeMentri served as anchor for the early evening newscasts as well as ones produced for WPHL-TV by the station.
In September 2012 DeMentri was again able to take to the airwaves when he was hired by Sinclair Broadcasting to anchor the evening newscast at WICS-TV in Springfield, Illinois even though questions arose through local newsprint media regarding his past history.
DeMentri was responsible for an investigative story that ultimately shed light on shredding practices occurring at the Springfield Police Department in an attempt to possibly obscure possible command personnel misdeeds regarding an off duty incident in Missouri. The story entitled "Ready, Set, Shred," or colloquially and locally known as "Shredgate," and may have ultimately been responsible for the resignation or early retirement of several members of command staff of the Springfield Police Department. Dementri continued his "hardball" type of investigative journalism and eventually engaging in surprise interviews of then Springfield Mayor J. Micheal Houston regarding the "Shredgate" scandal. Dementri continued to highlight the scandal and was later blamed by Houston for his ultimate loss in the election. 
However, Mayor Houston was not the only casualty on election night. DeMentri himself allegedly engaged in a reported physical altercation with another station personality while at a local restaurant causing law enforcement to be called and within days both TV personalities were terminated.
- "Vince DeMentri". Personalities. NBC10.com. Retrieved 2006-07-28.
- "The Investigators: Vince DeMentri". NBC10.com. 2006-03-24. Retrieved 2006-07-28.
- "Full Cast and Crew for U.S. Marshals". Internet Movie Database. IMDb. Retrieved 2006-07-28.
- State Journal Register (September 19, 2012). "New WICS anchor has long resume, history of controversy". www.sj-r.com.
- WICS TV (July 19, 2013). "Ready, Set, Shred". WICS-TV channel 20.
- 98.7 WNNS Radio (February 25, 2015). "Houston: Document Release "Exonerates" Him; Blames Shredgate Coverage For Primary Loss". www.wnns.com.
- WMAY Radio. "DeMentri, Reporter Out At Channel 20 After Altercation". www.wmay.com.