Mancini pounces for Pizarro from Roma
Pizarro shone on occasions for Mancini's Inter Milan in 2005/06 but after three good seasons at Roma, injury and fallouts with managers started to cut his appearances.
"Pizarro, I know him very well, he is a good player and a good midfielder," Mancini told Sky Sports after the 1-0 league defeat at Everton.
The diminutive 32-year-old will offer competition for places in central midfield as City seek their first top flight crown since 1968.
Yaya Toure is still away at the Africa Cup of Nations, Gareth Barry has been steady if unspectacular while Nigel de Jong and Owen Hargreaves have had few opportunities to impress this term.