The 28-year old, who was signed by the Baggies on the back his heroic efforts with Wales at Euro16, scored three goals in 28 appearances last season.
"I'm delighted because it's an opportunity to build on the good work we did last season and now I'm just looking forward to the new one," said Robson-Kanu.
"It was an easy decision. I've enjoyed my time here playing under Tony Pulis.
"It was a strong season and I want to build on the good work and contribute to a more successful future."
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