More than three-quarters (78%), of 1,500 students questioned, had lost money through unfair charges by landlords or utility companies.
Overall they lose £335m a year, says consumer mediator Ombudsman Services.
Students should be able to stand up for their rights, said chief ombudsman Lewis Shand Smith.
Energy, property and telecoms are the most likely culprits, suggests the research, with students reporting being overcharged for gas and electricity, made to pay bills from previous tenants or for damage they or their housemates did not cause.
Some forgot to reclaim their tenancy deposit or paid twice for the same service.
Only a quarter of students who encountered a problem actually complained, according to the survey. Some said they could not be bothered, while others were afraid of intimidation or embarrassed.
A new guide to help students avoid being overcharged contains tips on how to take a meter reading, shopping around to get the best utility deals,  querying high bills and how to report faults, keep records of conversations and complain.
Broadband packages are another minefield, says the guide, so students are advised to check the length of contracts, whether they are transferable, and to be aware of any limits on the amount of data they can download - even with so-called "unlimited" deals.
To avoid losing deposits for damage caused by previous tenants, they are advised to check tenancy agreements and take inventories and photographs when they first move in.
"We want to ensure that all students are able to stand up for their rights and speak out when things go wrong, whether that is being asked to pay for a bill from a previous tenant or paying for damage they did not do," said Mr Shand Smith.
"Students should not be losing money, simply because they don't know their rights or are not making a fuss."
Students are being left an average of £240 a year out of pocket because they are afraid to complain or do not know their rights, research suggests.