Al Harrington Gives 4/20 Advice, 'Get High As F***'

Ex-NBA hooper and current weed entrepreneur Al Harrington has some solid advice for any newbies looking to celebrate the 4/20 holiday this year ... telling TMZ Sports it's pretty simple -- "get high as f***!!!"

Harrington knows his stuff -- the guy built an entire company around his love for Mary Jane ... serving as the CEO of the Viola brand.

He's doing pretty well for himself, too ... with the company valued at over $100 million.

Harrington -- who played 16 seasons in the league for a number of teams -- told us he'll be in NYC for a three-day "4/20 Tour" this weekend ... 'cause apparently, the dude needs way more than 24 hours to show his love for cannabis.

Harrington has been a huge advocate for the benefits of marijuana -- in 2017, he sat down with former NBA commish David Stern ... and the conversation helped the league eventually take weed off the banned substances list.

As for folks looking to dabble with some doobies, Harrington says there's no need to complicate it ... just puff, puff, pass and enjoy yourself.