The University of Aberdeen compared clinical strains of the pathogen from the Grampian area with strains isolated from chickens, cattle, sheep, pigs and wild birds.
Food Standards Scotland said the findings will help develop a new Campylobacter strategy for the country.
The proportion of cases attributed to chicken decreased from 55-75% to 52-68% when compared to data from 2012-2015.
Other sources of infection are 14-26% for sheep, 9-11% for cattle, 1-2% for pigs and 7-8% for wild birds.
Virtually all broiler farms were positive for Campylobacter indicating more needs to be done on-farm to minimise risk of human campylobacteriosis, said researchers.
There are typically 43,000 cases and 500 hospitalisations due to foodborne illnesses in Scotland each year.
In 2016, 5,296 lab reports of Campylobacter infection were notified to Health Protection Scotland.
Campylobacter isolates were collected from clinical cases from April 2015 to December 2016, from abattoir sampled whole birds (representing retail ready chicken) and caecal samples (representing the farm environment).
Around half of the flocks were treated with at least one antibacterial agent which can lead to emergence of resistant strains and persistence in the poultry chain or farm environment.