The 37-year-old defender made the announcement after defeat to SPAL.
Barzagli said: "I thought a lot about my future, it's time to close my career: I will start a journey to understand what to do after a career in the next few months.
"I will evaluate among the options that most excite me.
"There is some confusion, in the coming months I will think about it well, I have to understand what I am capable of, which is functional for me and for a society, or for me, playing football was my dream as a child, it was what I wanted and I did it with enthusiasm.
"Now I have to find something that gives me as much enthusiasm."