Look at the colors on the football jersey. A fake jersey will have colors that are more dull and faded than the colors found on an authentic jersey. Be aware of the exact colors of the football team so that you will be able to tell the difference in color shades.
Hold the jersey in your hand and feel the fabric. An authentic football jersey will feel tighter than a fake. The counterfeit football jersey will also hang lower when worn, because it is a looser-fitting jersey.
Examine the "NFL" shield on the front of the jersey. The shield should be precisely placed in the middle of the V-neck. The middle of the football inside of the shield should have stitches so that it looks like an actual football. The shield on many counterfeit jerseys is wider than the actual NFL shield.
Notice the width of the shoulders on the football jersey. Authentic football jerseys are made to be exact replicas of what the players wear on the field. This means that the shoulders are wider, in order to fit shoulder pads. A fake jersey will fit your shoulders in the same manner as a shirt or sweatshirt.
Look for any mistakes made on the patch that is located on the bottom right portion of the front of the football jersey. Read over each word and look for any misspelled words. Examine the NFL logo that is on the left side of the patch, looking for the same mistakes indicated in step 3.
Check the numbers and name on the football jersey. These should be stiff, almost like cardboard, and completely attached to the jersey. Wrinkles in the letters or numbers indicate that the jersey is counterfeit.
Try to find any mistakes in the stitching. Loose stitches around the name or numbers as well as on the inside of the jersey are a sign that the football jersey is not authentic.