Defending champions Spain missed a penalty and then conceded a late goal as Croatia came from a goal behind to snatch a 2-1 win – and the top spot in Group D.
Elsewhere, Turkey beat the Czech Republic, which was enough to secure Northern Ireland's progress to the knock-out stages – despite their 1-0 loss to Germany earlier in the day that saw them finish in third in Group C.
Northern Ireland manager Michael O'Neill says his players have earned the right to be in the last 16.
A 1-0 defeat to Germany meant they finished third in Group C but progressed thanks to a 2-0 win for Turkey over the Czech Republic in Group D.
O'Neill says an alternative approach will be required for the knockout stage for a nation their size.
