This depends on whether you are going to install a car alarm by yourself or if you’re going to have it professionally installed. If you’re confident in your skills, then the cost is going to depend on the alarm you pick. Based on our research, the price can range from as little as $30 to as much as $200 or more. But if you opt to have a car alarm professionally installed, the price could be significantly more and may vary depending on which installer you hire.