Their 11th home defeat of the campaign was assured as early as the 13th minute when their now customary dismal defending saw the visitors open up a two-goal advantage.
It was spectacular even by Harriers' depressing defensive standards as Grimsby had not won in their previous eight starts.
Kidderminster must now prepare for life back in the Conference after a five-year Football League flirtation.
But on this evidence, they will continue to struggle and Stuart Watkiss has a mammoth summer task on his hands.
Watkiss has tried everything to pull the club out of free-fall but now faces the biggest test of his career as he tries to rebuild a shattered team with a drastically reduced budget following their League exit.
Kidderminster's tendency to slip into self-destructive mode continued in this final home game.
Their marking was non-existent in the eighth minute as Rob Jones rose unchallenged to head home Ronnie Bull's free-kick.
The home defence went to sleep again five minutes later allowing Michael Reddy to run 40 yards before slipping the second goal past the helpless John Danby.
Watkiss sent on striker Gary Birch at the start of the second half and he pulled a goal back in the 47th minute with a smart volley from Dean Keates' free-kick.
But the two-goal deficit was restored within a minute, Reddy cutting back a cross for Andy Parkinson to dart in and head home at the near post.
Grimsby's fourth came 12 minutes from time when another poor clearance saw Reddy gain possession and crash in an excellent 15-yard volley.