Grabban spent the first half of the season on loan at Sunderland and, despite the Black Cats’ struggles, he managed to score an impressive 12 goals from 19 Championship appearances.
The 30-year-old, who returned to the Vitality Stadium for a second spell in 2016, was recalled by the Cherries this month and manager Eddie Howe has confirmed the striker will be sold permanently.
A number of teams are said to be showing an interest in the Englishman and it was rumoured Wolverhampton Wanderers were leading the race for his signature at one stage.
However, reports are now claiming Cardiff, who are sitting third in the table, have moved to the front of the queue and a deal is expected to be wrapped up in the next couple of days.
Watford boss Javi Gracia does not think Abdoulaye Doucoure's form will be affected by his omission from France's latest squad.