The 29-year-old arrived in England on Monday and he is now set to put pen-to-paper on a three-year deal after agreeing terms with Rovers.
It is expected that Blackburn will now confirm the deal in the coming days before officially presenting him on Monday.
His British representative Barry McIntosh confirmed that the deal was in place.
"Mariano is delighted to get his chance in English football, he has spoken to several clubs but he was particularly impressed by Steve Kean," McIntosh told skysports.com.
"Steve made him feel very welcome and explained his plans, and Mariano was delighted with what he heard.
"He is now looking forward to the next chapter with an ambitious club like Blackburn."