The 30-year-old last season had a three-month loan spell at Leicester Tigers as temporary cover for injured England international locks Geoff Parling and Louis Deacon.
Gulliver's stature - he stands at 6ft 5in tall and weighs 17st 5lbs - makes him a big threat at line-outs and he was one of the vice-captains at Pirates, leading the side on several occasions.
The lock began his career at Coventry and following a spell at Saracens - where he represented England Students - Gulliver made the move to Plymouth Albion.
Gulliver moved to Albion's local rivals Cornish Pirates in 2008 and played a major role in the club lifting the inaugural British & Irish Cup in 2010.
Head Coach Richard Hill revealed he has tracked Gulliver for a number of seasons and was delighted to finally get his man.
"I have been watching Ben for a long time and I have twice looked to sign him before, only for him to suffer an injury, so I'm delighted to finally sign him up," he said.
"He impressed me at Coventry and when Graham Dawe signs a forward you know they are a good one because he has a very good eye for a talent.
"Ben was on loan at Leicester last season and he played against in the A League and had a very good game for Tigers.
"Ben also impressed when playing for Pirates against Warriors. He is a very hard, abrasive, combative and aggressive forward that caused us problems.
"He is physically very strong and athletic for a big man. I am very sure Ben will make the step up to Premiership level next season with the Warriors."
Gulliver is the 11th new signing at Warriors and is joined by Shaun Perry, Danny Gray, Ceri Jones, James Percival, Chris Jones, Ollie Hayes, Errie Claassens, Josh Drauniniu, Sione Tu'ipulotu and George Porter.