Niang is on loan at Vicarage Road from AC Milan and Watford have an option to sign the 22-year-old French striker on a permanent basis for £13.5million at the end of the season.
Mazzarri, speaking ahead of tomorrow’s trip to Hull City, said: “There are a lot of factors involved but we really hope to keep him.
“If he plays like he did in the last two matches, I would really like him to stay.”
Meanwhile, Mazzarri is "100 per cent" certain he will be still be the manager at Watford next season after all-but securing the club's Premier League status for another year.
The Italian faced an uncertain future following a string of poor results.
But his Watford side reached the magic 40-point mark with victory against Swansea last weekend and will head to Hull 10th in the table following three victories from their last four games.