It was the third time in less than a year that the 52-year-old had been fired -- he was sacked twice by Palermo last season, first in November and again in March after being recalled in February.
Iachini was appointed by Udinese in May following the end of the previous season and took charge of only eight competitive matches during his five months at the helm.
"Udinese have relieved Giuseppe Iachini of his post as coach of the first team," said the club in a brief statement.
In his 15-year coaching career, Iachini has done the rounds of some of Italy's less fashionable clubs.
He has had two stints each at Brescia and Palermo and also coached Venezia, Cesena, Vicenza, Piacenza, Chievo, Sampdoria and Siena. He has won promotion to Serie A with Brescia, Chievo and Sampdoria.
Udinese are 16th in Serie A with seven points from as many games.
The only other coach to lose his job in Serie A this season so far was at Palermo where Davide Ballardini was replaced by Roberto De Zerbi.
(Writing by Brian Homewood; Editing by Clare Fallon)
