Willem II staged a late comeback to inflict a first Eredivisie defeat on Heerenveen since the opening day of the season.
The visitors to Tilburg took a 41st-minute lead through Mark Uth, but Stijn Wuytens and Terell Ondaan scored in the last 15 minutes to earn Willem II a 2-1 win.
Heerenveen were on course to climb to the top of the table when in-form striker Uth produced a tidy finish to net his fifth goal in eight games this campaign.
Newly-promoted Willem have found goals harder to come by in their inconsistent return to the top flight, but Wuytens and Ondaan both opened their accounts for the season to cause somewhat of a surprise result.
Ondaan's 87th-minute winner secured Willem their third win in four games and takes them to eighth in the table.
