The loosehead will follow the path also taken by Sam Betty and Blair Cowan in recent years by swapping the south coast for Sixways and is eager to make the move a big success.
"I'm really excited and happy to have the chance to come to Warriors and have a crack at the Aviva Premiership," said Andrew.
"I know the Warriors from their season in the RFU Championship and played in all three games against them and have seen how the club is progressing. I remember the awesome atmosphere when I played at Sixways and it will be great to enjoy that again.
"I'm really sad to be leaving the Pirates, my first professional club who gave me my chance. But the chance to try top-flight rugby is massive," he added.
"I'm a Cornishman and proud of that. I have a lot of family here and it was gut-wrenching to make the decision to leave. But I want to play at the highest level and I look at what Sam and Blair have done. It would be great to follow in their footsteps so it's a no brainer.
"There is still much to play for this season and I will keep giving everything for the Pirates.
"The squad want to win every game and really achieve something at the end of the year. We have the cup and also the play-offs to target so lots to do before I can focus on Warriors."