Jenelle, 21, is already mum to son Jace, however her own mother is raising him after she lost custody due to her wild behaviour.
The pregnant star announced her and boyfriend Nathan Griffith's baby news at the end of last year, however she has now revealed its sex and shared a scan picture.
In an interview with Us Weekly, Jenelle said: "I was happy either way no matter what we were gonna have, but Nathan was especially excited because he's a boy, so he was like jumping for joy."
She added: "[Jace has] been talking about how he can teach him little boy things now."
In the last three years, Jenelle has been arrested 10 times for an array of offences, including heroin possession, disturbing the peace and making harassing phone calls.
In 2012, she married Courtland Rogers but their volatile relationship didn't last. Last year, Jenelle was shown on Teen Mom 2 deciding to have an abortion.
Although she is still legally married to Courtland, Jenelle - who is off drugs and training to be a medical assistant - is now loved-up with Nathan and they are both looking forward to their new arrival.
Sharing a scan pixture on Twitter, Jenelle said: "Mommy and daddy's pride of joy. Daddy and I can't wait to finally meet you."
Jenelle has also hit back at one follower who messaged her saying: "You couldn't even take care of one kid, how ya gonna mange two?" Jenelle replied: "We shall see, won't we?"
Are you a Teen Mom fan? Tell us below, as the best comment from across the website each week wins £50.