Pretorius-born Poolman has excelled for the Stormers in an international back-line that includes Jean de Villiers, Bryan Habana and Gio Aplon.
Hailing from the famous rugby school Paul Roos Gymnasium, the powerfu 23-year-old is an exciting prospect who already has serious rugby pedigree, scoring a try in the Vodacom Cup final to help Western Province beat the Griquas to lift the 2012 title.
At 1.89m and 100kg, Poolman is a sizeable yet deceptively nimble centre who can also play on the wing and with the three-year deal could qualify to play for Ireland in years to come.
He will be joining a settled Connacht side which has been strengthened by some astute signings in recent months.
When the RaboDirect PRO12 kicks off in September, Elwood will be able to call on Heineken Cup finalists Nathan White and Willie Faloon, as well as former Scotland international Dan Parks.
Poolman's signing is further indication of the hard work that is going on off the pitch to strengthen the depth of this Connacht side for the rigours of the league and their second Heineken Cup campaign.
With the emergence of Academy stars such as Denis Buckley, Michael Kearney and Shane Layden, coupled with the experience of Connacht legends John Muldoon, Michael Swift and Gavin Duffy, the new signings will help to shape the future of the team in an exciting time for the development of the province.
Speaking about the signing, Elwood said: "We are delighted to be signing a young exciting prospect such as Danie who has already gained valuable Super 15 experience.
"He's coming from a club with an excellent reputation for developing young talent and he has starred alongside some quality international players.
"He's a strong ball carrier with an excellent work-rate both in attack and defence and I am really looking forward to working with him."
Poolman added: "I am very excited to be joining up with Connacht. I am looking forward to learning from their coaches, players and structures.
"It will be a truly international experience, I think of Ireland as a long-term goal, and I am confident I can add value to the squad for next season's league and Heineken Cup campaign.
"I am grateful and want to thank Western Province for all that I have learned and achieved, but this is really an once-in-a-lifetime opportunity...to be able to experience life and rugby in beautiful Ireland!"