The 40-year-old has been in charge at Tannadice since January 2013 and his side currently occupy fourth place in the SPFL Premiership.
The former Scotland internationalist has overseen impressive form on the pitch, although his tenure has also been marked by the emergence of such as Ryan Gauld, John Souttar and Ryan Dow. It is his relationship with the club's brightest young talent which has allowed McNamara to become a valued coach at the club.
He was also keen to extend his contract at a club where he is settled. "My relationship with the board of directors and the chairman is the strongest I have experienced in football, and working with the quality players available to me at Dundee United makes the job enjoyable," said McNamara.
"Signing this extension is one of the easiest decisions I have made as a manager. We have made a lot of progress in the first year here but can achieve a lot more."
That sense of ambition continues to impress the United board. "We are excited by the job that Jackie has been doing and his desire to build strong foundations is in line with how we see the club progressing," said Stephen Thompson, the United chairman.
"His commitment to developing young players and giving them the chance to prove themselves on the park is creating positivity for the future and entertaining the fans."