Avoid supporting his immaturity in any way. Supporting or enabling behaviors such as immaturity can often be a sign of a dysfunctional helping relationship, according to professor of psychology Shawn Meghan Burn in her article "Are You in a Codependent Relationship?" on the "Psychology Today" website. For example, rescuing your guy from predicaments that his immature behavior has gotten him into -- such as an argument with a member of one of your families or a situation at work -- is off the table. While it may seem like you're helping him out of a sticky situation, you're actually making him believe that it's acceptable to act immature. Let him take the fall for his immaturity.

Pinpoint how and when he is being immature. There are many different ways that a boyfriend could act in a childish way. For example, not wanting to work is a sign of immaturity, but so is making jokes instead of speaking his feelings. The way that he is being immature will impact how you deal with him and what changes you can expect.

Step up and show an assertive style. If your guy's immature actions are truly bothering you, let him know that his behavior is a problem for you and your relationship. He may not realize that he's acting immature or he may not know that it is affecting you. This doesn't mean that you aggressively confront him. Instead, tell your guy how you are feeling, being specific about how he's immature and what it is doing to your relationship. For example, say something such as, "When you spend Saturday afternoons playing video games with your friends instead of with me, I feel like you are acting childish. This hurts my feelings and makes me worry that we don't have a real future together."

encourage him to do things for others. Some emotionally immature men are narcissistic or act childish in a selfish way. If this is the case with your boyfriend, organize a volunteer outing in which he's faced with the realities of adult life. For example, serve soup at a homeless shelter or help out at a food pantry on a holiday.

Stop and point out his childish behaviors. If he isn't aware of or doesn't believe he is acting immature, show him. Tell him that he's acting like a child when you catch him in the midst of acting immaturely or record his behaviors on a video camera or with your cellphone. Play the video back to show him how he is acting and how other people around him view him.