Born in the USA, Black qualifies for Ireland through his paternal grandfather who was from Belfast and joined Worcester straight from Hartpury College in Gloucestershire.
"This is a new and exciting challenge for me"commented Black.
"I'm at the stage in my career where I'm looking to really push on and I'm really looking forward to playing in the Magners League and Heineken Cup"
"I've watched Ulster this season and been very impressed with how the team is developing and I'm looking forward to being part of that."
"My goal is to establish myself in the Ulster team and then try to force my way into the Ireland set up."
McComish will join Ulster from Connacht where he has played for the past two seasons. He is an accomplished Number 8 but can play anywhere in the back row.
A former development player within the Ulster Squad, he had spells with both Rotherham and Otley in England before joining Connacht ahead of the start of the 2009-10 season.
McComish attended Campbell College and went on to play a key role in the Ballymena team that won the All Ireland Division One league in 2004. The 27 year old has played for Ireland at U-21 level and has also represented the Ireland 7's side.
"We're delighted to announce that Callum and Michael will be joining us and strengthening our squad ahead of next season," said Ulster director of rugby David Humphreys.
"Having spent the last few seasons with Connacht, Michael has gained a lot of Magners League experience while at just 25, Callum has ammased considerable experience from the Premiership, the Championship as well as the LV and Amlin Challenge Cup competitions and so will be a very useful addition to our front row."