Former South Africa international seamer Charl Willoughby has signed a two-year deal with Essex after leaving Somerset earlier this month.
The 36-year-old took 347 first-class wickets for Somerset, where he spent six years following his move from Leicestershire in 2006.
"Essex made a concerted effort to come and meet me," he told the club website.
"[Head coach] Paul Grayson and myself had a long discussion and we discussed my aims and that of Essex."
He added: "I obviously have a lot of experience in the game and Paul Grayson wants a wise old head to help David Masters with the bowling attack.
"Essex have some promising youngsters coming through the ranks and I can certainly pass on some of my knowledge as a left-armer."
Willoughby, who has two Test caps, took 47 wickets in 14 County Championship matches in 2011 at an average of 34.65.
"He is a very experienced bowler and someone we wanted to add to our ranks alongside David Masters and Graham Napier," added Grayson.
"He is a quality left-arm bowler and we see him also helping Reece Topley and Tymal Mills in their development with his experience and knowledge of the game."