Di Carlo became the third boss to be sacked by Livorno this season when his 88-day reign was abruptly ended following Saturday's 3-0 defeat at AC Milan.
Nicola, who was axed by the club in January, will now have four games to attempt to save the Tuscany outfit from relegation.
"Livorno officially announce that we have dismissed Domenico Di Carlo as coach of the first team," read a statement on the club's official website.
"The club wishes to thank to Mr Di Carlo for his dedication and professionalism and the work undertaken.
"The post of coach of the first team of Livorno Calcio has been entrusted to Davide Nicola."
Livorno are currently 19th in the Serie A table, three points from safety.