The Italy international was a City target last year, but Mancini believes his team has the goalkeeper position covered by the talented Joe Hart.
Mancini told Turin-based sports newspaper Tuttosport: "The way I see it is that Buffon remains one of the best goalkeepers in the world.
"But we have decided for some time to point on Hart, who is a young player with enormous potential. We believe so much in him to the point of having sacrificed a great number one like (Shay) Given.
"Hence, I can categorically say that we will never make any offers for Buffon."