Van der Merwe joins the GUINNESS PRO12 side from South African outfit Golden Lions, for who he made 99 appearances.
And the 31-year-old, who made his only appearance for the Springboks against New Zealand in 2013, says the glowing references from Ulster's other South Africans helped him make the decision to switch to the Northern Hemisphere.
"Moving out of South Africa to somewhere totally new is the biggest step of my career," he told the Ulster website.
"My wife and I are so excited to come to Ulster. We have heard so many good things from previous players, from Johann [Muller] and Ruan [Pienaar], everyone is just so positive and they speak so well about the Province.
"In terms of rugby, there is no reason for me to come here and to try and reinvent the wheel. I can only do the basics. I am here because of what I did in South Africa so I am going to do the same things again.
"I hope that it can stay like this for quite a while but everyone was saying that it is always raining here. I don't know what everyone was complaining about! It's really nice to see the sun. I am enjoying the beautiful weather and I am enjoying the beautiful scenery."
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