North Yorkshire Police said three homes in the Starbeck and Granby areas were targeted overnight between Sunday and Monday.
Items stolen included purses, wallets, mobiles, tablets and cash.
The homes burgled were in Avenue Street, Greenfields Avenue and Wedderburn Road.
It is believed that thieves gained entry through unlocked doors and windows.
Inspector Penny Taylor, of the Harrogate South Neighbourhood Policing Team, said: “Whilst Harrogate is a safe area, the number of burglaries does unfortunately tend to increase over the summer months.
“With the warmer weather residents may inadvertently leave doors and windows open, which then leaves their property at risk of an opportunistic thief.
“We advise that all residents check their windows and doors each night before going to bed, to ensure that their home is secure.”