The troubled basketball star checked himself into a treatment facility in San Diego, California last month (Dec16) in a bid to maintain his sobriety, and spent Christmas and New Year under doctors' care.
He has since completed his 35-day stay and is due to return to Los Angeles on Thursday (05Jan17).
"Lamar is leaving rehab today," a source tells People.com. "He's doing great and he's happy. He's heading home to L.A. He has the support of friends and family and his kids visited him last week."
Lamar reportedly sought out professional help amid fears the December (16) birthday of his late son Jayden would prompt a relapse. He lost his boy, his third child with ex-girlfriend Liza Morales, in 2006, when he was just six-months-old.
The sportsman was also reportedly struggling to deal with the end of his marriage to Kim Kardashian's sister, after their divorce was finalised at the end of the year (16). The former couple split in 2013, but Khloe put her divorce plans on hold in October, 2015, after Lamar suffered a drug overdose at a brothel in Nevada and was hospitalised for several weeks.
She refiled her legal papers in May (16), after nursing him back to health.
The news of Lamar's rehab completion emerges shortly after Khloe gushed about finding happiness again, thanks to her new romance with another basketball star, Tristan Thompson.
The pair began dating in September (16) and the reality TV star and fashion designer is feeling better than she has in a long time.
"At this moment, a few days into 2017, I feel incredibly clear and probably the happiest I've been in years," she told fans online."