The Carmarthen born speedster came through the Scarlets youth system and made four senior appearances for the region, before playing in the English Championship with London Welsh.
He then spent three seasons at Neath with an outstanding record, helping the Blacks to 47 wins in 69 games in all competitions, scoring 19 tries in the process.
A Wales international at Under 18, 19 and 20 level as well as with Wales Sevens, Jenkins was a member of the Under 19 Grand Slam-winning side of 2006 which included recent full Wales internationals Jonathan Davies and Bradley Davies.
“I played with Alec here at Neath and he’s an outstanding rugby player and outstanding bloke,” said Neath coach Neil Edwards.
“He gives 100 per cent and was disappointed to have left the club last year. He’s really looking forward to coming back and proud to be a Neath man again.
“He’s a big winger and he’ll do his job all the time. I’m confident we’ll have good displays from him next season.”
