3:10 PM PT -- Dana Carvey says Dex Carvey died of an accidental overdose. He and his wife Paula just posted a note remembering their son's talent and passion for life, and says "We will miss him forever."

They add, "To anyone struggling with addiction or who loves someone struggling with addiction, you are in our hearts and prayers."

Dana Carvey's eldest son, Dex Carvey, has died ... TMZ has learned.

Law enforcement sources tell us Dex passed away Wednesday night after first responders rushed over to a home that his girlfriend had called from in Los Angeles around 10 PM. We're told Dex was locked in a bathroom, and that he was unresponsive upon discovery.

Our sources say paramedics tried reviving him, but to no avail ... he was pronounced dead on the scene. An autopsy has been done, but Dex's cause of death hasn't been determined ... pending toxicology tests.

Dana and Dex were very close ... in fact, Dex was following in his father's footsteps when it came to comedy -- as he was diving into the stand-up world over the past few years.

Dex actually opened for his father in his 2016 Netflix special, 'Straight White Male' ... during which Dex did a 6-minute set that got some laughs as he worked on material -- touching on a number of topics ... including pride parades, cult stories and his famous dad.

Dana's other son, Thomas, is also an aspiring comedian ... and the former 'SNL' star has spoken fondly of his boys and wanting to help their careers. Dex was only 32.

RIP