The Welsh star and 27-year-old Yallouz will tie the knot in the summer of 2013, according to Entertainment Tonight.
Yeoman and Yallouz, a jewellery designer, have dated since early this year.
The actor has played California Bureau of Investigation agent Wayne Rigsby for nearly 100 episodes on The Mentalist, which premiered in 2008.
Yeoman previously appeared on the HBO miniseries Generation Kill and the British programme Midsomer Murders.
He is a graduate of the Royal Academy of Dramatic Arts in London.
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