Fence posts are set far into the ground when installed to keep them from leaning or heaving. Heavy winds, flooding and freezing weather can move fence posts, even if installed in concrete. A leaning post will ruin the fence line and weaken it, making further damage a distinct possibility. Most problems are solved with a little digging and possibly the addition of some concrete to the hole. Before calling out a professional, try resetting the post yourself.
Dig dirt away from the side the post is leaning toward, and have a work partner hold the post in place.
Straighten the post by hand and backfill the hole with the dirt to keep it standing.
Rip out the nails of the surrounding fencing if the post continues to lean after a hard frost. This is called heaving. Remove the fencing according to your fence type.
Dig dirt up from around the post and remove the post with the concrete from the ground. Break away the concrete with a sledgehammer.
Remove dirt from the bottom of the post hole so that the hole is deeper than the frost line -- between 42 and 48 inches.
Mix together some quick drying cement according to the instructions on the label.
Place the post in the hole so it is straight and fill the bottom of the hole with a few inches of gravel. Pour the quick drying cement into the hole and allow it to dry.
Fill the rest of the hole in with dirt.