Danny Rowe capitalised on the defender's error to cancel out Shamir Fenelon's opener but Evans headed in late on for the three points.
Both sides finished the match with ten men - first Jack Muldoon was sent off for the visitors in the second half for an off the ball incident before Aldershot sub Manny Oyeleke saw red.
The result has put Gary Waddock's side back into the play-off places and left Evans relieved, he said: "I wasn't having the greatest of games. My man scored for their goal so it was a good feeling for me to get the win and the goal.
"I kept saying to Adam [McDonell] 'put it at the back post' about four or five times but he kept hitting the front post. I'm glad Rends [Scott Rendell] flicked it on and it eventually got to the back post and I headed it in.
"It was one of those that you keep your eye on it and you know where the goal is because you're that close to it."
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