This is their first title since 2014 and a record-extending 34th overall completed the double after they won the KNVB Cup earlier this month.
Ajax had been neck-and-neck with PSV over the last weeks, but made all but sure of the title on Sunday when they beat Utrecht while defending champions PSV lost.
They ended three points clear of PSV Eindhoven, who won 3-1 at home to Heracles Almelo on the last day of the campaign.
Dusan Tadic scored twice against De Graafschap as Ajax said farewell to key midfielder Frenkie de Jong, who is joining Barcelona, and possibly several other players who are in demand following Ajax’s superb run to the Champions League semi-finals.
Ajax ended with 86 points and 119 goals scored in 34 games. PSV collected 83 points to join them in next season’s Champions League.
Feyenoord came third after winning 4-1 at Fortuna Sittard, the last game in charge for their coach Giovanni van Bronckhorst.