The actress will play Loraliei Martins, a new love interest for Simon Baker's character Patrick Jane.
According to TV Line, Loraliei will have a mysterious side and appear "too good to be true".
Chirqui will make her Mentalist debut in the season four finale on May 17 and appear in at least five episodes of its next run.
As well as Entourage, she has appeared in The Borgias and lent her vocals to the recent Thundercats reboot.
The Mentalist airs Thursdays at 10/9c on CBS.
> Emmanuelle Chriqui: 'Entourage final season was tough'