Getty ImagesWritten prescription fees from vets will be capped at £21 and practices will have to publish price lists for services, the UK's competition watchdog has said.
The Competition and Markets Authority (CMA) also said a price comparison website would be introduced to help boost competition and drive down prices faced by consumers.
The measures come after an in-depth investigation by the watchdog, which found prices had been rising at nearly twice the rate of inflation.
The CMA said the reforms would start to come into force later this year.
Vets will also have to reveal if they are part of a large group, following concerns that ownership of practices was unclear.
About 60% of UK households own a pet, and the CMA says the vets sector is worth more than £6.7bn.
Martin Coleman, chair of the independent Inquiry Group, said: "Today's reforms will make a real difference to the millions of pet owners who want the best for their pets but struggle to find the practice, treatment and price that meets their needs.
"Too often, people are left in the dark about who owns their practice, treatment options and prices – even when facing bills running into thousands of pounds.
"Our measures mean it will be made clear to pet owners which practices are part of large groups, which are charging higher prices, and for the first time, vet businesses will be held to account by an independent regulator."
The CMA found that more than 70% of pet owners bought long-term medication from their vet practice even though many could save £200 a year or more if they looked online.
As part of the reforms, pet owners must be told they can have a written prescription which could save them money.
Prescription fees are currently uncapped, but will be capped at £21 for the first medicine and at £12.50 for any additional medicines under the reforms.
Under other measures set out by the CMA
Kelly Norton, 50, spends a good chunk of the year travelling around Europe in her camper van along with her husband and their 11-year-old dog Vinny.
After their vet in the UK found a non-cancerous tumour under Vinny's armpit, they were quoted £1,600 to remove it.
Jim Connolly/BBCWhile on a trip to Italy, Kelly took Vinny to a local vet. She was told the operation would cost €160 (£138).
"I don't understand how it can be so cheap, but here in the UK everything costs 10 times as much," Kelly says, calling the cost difference "atrocious".
Kelly says she's lucky she can travel for treatment.
"It makes me really angry that some people have to surrender their dogs or have them put down because they can't afford the cost in the UK," she adds.
Additional reporting by Jim Connolly & Abi Smitton, BBC News Investigations