Under an amendment to a new law on tourism adopted by the regional parliament, the hotel-owners concerned would no longer be eligible to take part in tenders for business from the local authority.
The measure is the latest sign of tension between several Italian regions where the far-right wields considerable political influence and the centre-left government over the distribution of migrants to reception centres and temporary facilities across the country.
The Lombardy move was backed by regional governor Roberto Maroni's anti-immigrant Northern League and the centre-right.
Other parties opposed the move and have vowed to have it declared unconstitutional as soon as it is formally enacted.
The proposal stopped short of a demand by Northern League leader Matteo Salvini for hotel owners housing migrants to be stripped of their licences on the grounds that they are aiding and abetting illegal immigration.