The man, employed at the Ciaccio hospital in the southern city of Catanzaro, Calabria, is accused of not turning up for work since 2005.
Now aged 67, he is being investigated for fraud, extortion and abuse of office, Italian news agency Ansa reported.
He was reportedly paid €538,000 (£464,000) in total over the years he is thought not to have been working.
Six managers at the hospital are also being investigated in connection with the alleged absenteeism.
The man was caught out by a police investigation, codenamed ‘Operation Part Time’, into absenteeism and suspected fraud in the Italian public sector
He was reportedly assigned to the job in 2005, at which point he is alleged to have stopped going in.
He is also accused of threatening the hospital director to stop her from reporting his absenteeism.
After that manager retired, neither her successor nor human resources ever noticed his absence, police said.
In 2016 the Italian government tightened a law aimed at stopping absenteeism, after police uncovered a string of cases of public sector workers pocketing pay without turning up for work.