Vale refused to allow the visitors time to settle on the ball in a competitive and scrappy first-half.
The hosts bossed most of the play and forced a series of corners without seriously threatening to score.
An out of sorts MK Dons looked fortunate in the 30th minute when last defender Antony Kay escaped with a yellow card for a foul on Ben Williamson.
Vale remained in the ascendancy at the start of the second period and Louis Dodds should have done better than scoop his shot too high from Williamson’s pass.
Even a double substitution in the 62nd minute, when Lewis Baker and Rob Hall replaced Dele Alli and Dan Powell, failed to stir the Dons.
It was Vale substitute Mohamed Coulibaly who came closest to breaking the deadlock when his 71st-minute strike narrowly missed the target.
And impressive winger Mark Marshall almost won it for Vale deep into stoppage time when his close-range effort was cleared off the line by Lee Hodson.