Goals by Danilo Orsi and Klaidi Lolos in the first half earned the three points which were enough for Scott Lindsey’s team to finish seventh. They’ll play MK Dons in a two-legged play-off semi – and will be off to Wembley if they come through.
The home leg is on May 6, the away leg May 9.
Photographers James Boardman and Stephen Lawrence of Telephoto Images were there to capture the action and the great post-match scenes as fans invaded the pitch and the players and management came out into the stand to join in the fun.
See the best of their celebration and action pictures on this page and the ones linked – and be sure to get the Crawley Observer on Wednesday for all the action and reaction.
41. Crawley Town's Klaidi Lolos celebrates scoring 2-0
Crawley Town's Klaidi Lolos celebrates scoring 2-0:Action in the Crawley Town-Grimsby game that the Reds won to secure a play-off place Photo: James Boardman:James Boardman / Stephen Lawrence / Telephoto Images
42. Crawley Town take on Grimsby - and beat them to clinch a play-off spot (2).jpg
Action in the Crawley Town-Grimsby game that the Reds won to secure a play-off place Photo: Dov Friedmann:James Boardman / Stephen Lawrence / Telephoto Images
43. Crawley Town's Danilo Orsi celebrates scoring 1-0
Crawley Town's Danilo Orsi celebrates scoring 1-0:Action in the Crawley Town-Grimsby game that the Reds won to secure a play-off place Photo: James Boardman:James Boardman / Stephen Lawrence / Telephoto Images
44. Crawley Town take on Grimsby - and beat them to clinch a play-off spot (5).jpg
Action in the Crawley Town-Grimsby game that the Reds won to secure a play-off place Photo: Dov Friedmann:James Boardman / Stephen Lawrence / Telephoto Images