Tourists face fines of €25-500 if they fail to comply with measures, which also ban the use of loudspeakers.
Venice will limit the size of tourist parties to 25 people from Thursday in the latest attempt to reduce the impact of crowds on the lagoon city.
Local authorities will also ban the use of loudspeakers by tourist guides in measures aimed at “protecting the peace of residents” and ensuring pedestrians can move around more freely.
There will be fines ranging from €25-500 (£21-£422) for those who do not comply with the measures, which were originally planned to take effect from June but held over until the start of August.
The restrictions cover the city centre and also the islands of Murano, Burano and Torcello.
n April, Venice became the first city in the world to introduce a payment system for visitors in an experiment aimed at dissuading daytrippers from arriving during peak periods.
The pilot scheme, which has been watched closely by other European tourist hotspots, covered 29 days and ended in July, opening the way for a period of consultation to decide how to proceed with the project in future.