Aims: The objectives of this study were the following: (i) to investigate if Campylobacter negative flocks at first thinning remain negative at second thinning; (ii) to determine if the caecal counts in birds infected during first thinning remain lower than in birds that were positive at first thinning; and (iii) to determine if reducing the time between first and second thinning to a maximum of 4 days would reduce both the incidence and prevalence of broiler caecal contamination. Methods and Results: Twenty-two flocks were tested at first and second thinning using ISO methodologies. Of the 14 that had a 4-day duration between first and second thinning, nine flocks were Campylobacter negative at first thinning. By second thinning, all 14 flocks were positive and Campylobacter counts ranged from 5.5 to 6.6 log(10) CFU g(-1) regardless of the status at first thinning. The other eight flocks were all Campylobacter positive at first thinning with counts ranging from 0.8 to 6.1 log(10) CFU g(-1) which increased to 5.1 to 6.9 log(10) CFU g(-1) by second thinning (3-10 days). PCR speciation and MLST genotyping suggested the majority of isolates were Camp. jejuni belonging to STs 257, 814, 6763 and 6764. Conclusions: It was concluded that; thinning introduces Campylobacter into broiler flocks; caecal counts in birds at second thinning are similar, regardless of flock status at first thinning and reducing the time between first and second thinning to a maximum of 4 days is not an effective control strategy. Significance and Impact of the Study: This study informs Campylobacter control strategy at primary production, suggesting all post-first thinning broilers should be treated as 'high risk' regardless of Campylobacter status at first thinning or duration between first and second thinning.