The charity Victim Support said the overall decline in homicides is a "glimmer of hope" for an area of crime that leaves families with long-lasting trauma and grief.
Figures from the Home Office show there were three homicides recorded by Gwent Police in the year to June – up slightly from two the year before.
Homicide referrs to the offences of murder, manslaughter and infanticide.
The area bucks the trend across England and Wales, where the number of homicides decreased by 6%, with 518 offences last year.
It was the lowest figure since current police recording practices began in 2002-03, when the figure stood at 1,047 – although this includes 173 victims of serial killer doctor Harold Shipman.
Katie Kempen, chief executive at Victim Support, said: "While crime levels remain lower than a decade ago, millions of people continue to be harmed – and the impact on victims is life-changing.
"We know from our work delivering the National Homicide Service just how devastating homicide is for families and communities, the trauma and grief can be profound and long-lasting.
"It is therefore encouraging to see that homicide levels are at their lowest since 2003, offering a glimmer of hope in what remains a deeply painful area of crime.
"If the Government is serious about supporting victims, it must urgently reverse recent cuts and invest in long-term, sustainable funding for these vital services."
Other recorded crimes in Gwent included 4,622 shoplifting offences in the year to June, up slightly from 4,525 in 2023-24.
Across England and Wales, shoplifting rose 13% to 529,994 crimes in the recent year – just below the recent all-time high.
Billy Gazard, of the Office for National Statistics, said the data for police-recorded crime "paints a mixed picture".
He said: "While shoplifting continues to rise year on year, there are signs the rate of increase in reporting of these offences is slowing."
Crime and policing minister Sarah Jones said: "This Government is making real progress in protecting vulnerable young people, homicide rates have hit their lowest levels since the 1970s and knife crime is down after just one year in office."
"But we know that any life lost is one too many and we are not complacent as we seek to halve knife crime over the next decade."
She added: "We also know that the levels of shop theft and street crime that this Government has inherited are utterly unacceptable."
The British Independent Retailers Association said its own survey shows most crimes in shops go unreported because retailers have lost faith in police response.
Andrew Goodacre, chief executive of Bira, urged the Government to swiftly introduce its plan for a "Winter of Action" to renew the focus on shoplifting after its summer initiative.
He added: "Independent retailers are the backbone of our high streets and need visible support now to protect their businesses, their staff, and their livelihoods."