The Ben Kinsella Trust, which campaigns against knife crime, said the rate of reoffending shows investing in rehabilitation is crucial rather than "simply locking people up".
Figures from the Ministry of Justice show the Criminal Justice System dealt with 326 knife and offensive weapon offenders in Devon and Cornwall in the year to March.
Of these, 86 had a previous conviction or caution, meaning 26.4% were committed by repeat offenders.
This was down from 27.8% the year before.
Across England and Wales, 31.5% of knife and offensive weapon offenders had a previous conviction or caution – the highest rate since records began in 2014.
Subsequently, the rate of first-time offenders is at a record low, falling slightly to 68.5% last year.
Patrick Green, chief executive of the Ben Kinsella Trust, said: "The increasing number of repeat offenders with knife crime convictions is alarming."
He called for "crucial" investment in rehabilitation rather than simply locking people up to break the "cycle of reoffending" the figures expose.
The figures also show the overall number of knife and offensive weapon offences dealt with by the justice system in England and Wales fell 3.3% in the past year, from 19,200 in 2022-23 to 18,600 last year.
Yet, in Devon and Cornwall, it increased from a total of 349 offences to 362.
Mr Green said the fall in offences dealt with by the justice system shows a "concerning anomaly".
He said: "Office of National Statistics figure released last month show that knife crime offences have grown 4% in the last year, yet Thursday’s figures from the Ministry of Justice show a fall in number offenders being dealt with by the criminal justice system."
"This does raise questions about whether the full force of the law is being correctly applied in knife crime cases."
He added the "alarming statistic" of 3,206 knife crime offences committed by 10 to 17-year-olds is "deeply troubling". The number of these offences committed by under 18-year-olds has increased by 20% since 2014.
"It's clear we are moving in the wrong direction. To effectively address knife crime, we must prioritise preventing young people from becoming involved in such violence," he said.
In Devon and Cornwall, 15% of knife and offensive weapon offenders were 10 to 17 years old.
A Ministry of Justice spokesperson said knife crime is a "scourge on our society", adding the Government is dedicated to halving knife crime within a decade.
They said: "First steps will include making sure the tightest restrictions are in place to limit the sale of dangerous weapons, including banning ninja swords.
"We will also end the practice of empty warnings, ensuring carrying knives triggers rapid intervention and tough consequences."