Fusco had one year remaining on his deal at just under $1.4 million.
The extension is a good haul for a former sixth-round pick out of the most elusive university in Pennsylvania, Slippery Rock.
The one-time project has become a rock for the Vikings, starting 31 games the past two seasons. Pro Football Focus graded Fusco as their No. 8 overall guard and No. 3 right guard in 2013.