Both men have contracts until the end of the season, with Swansea announcing in a statement Monday that the 60-year-old Guidolin "will have the final say on team selection."Curtis took over as interim manager after Garry Monk was fired last month.
"Although we recently appointed Alan Curtis as manager until the end of the campaign, he was aware and comfortable with the fact that we were still looking to bring someone in to assist if we found the right person," Swansea chairman Huw Jenkins said.
"We believe we have found that person in Francesco".
Jenkins highlighted Guidolin's coaching experience and "knowledge of players throughout Europe, which will be a big boost on our recruitment side."
Guidolin's position will be reviewed at the end of the season, with the option of extending his contract, the club said.
Guidolin made his name in Italian football in the 1990s with Vicenza, winning the Coppa Italia and reaching a European Cup Winners' Cup semifinal against Chelsea, before going on to spells with Bologna and Udinese.
Swansea is battling to avoid relegation from the top-flight and needs a win later Monday at home Watford to move clear of the drop zone.
Guidolin will be at the Liberty Stadium to see the team in action.
Third from bottom in the standings, Swansea is currently two points adrift of 17th-place Newcastle.
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