First-year residents frequently encounter conflict during their training. Residents' conflict management strategies can influence patient safety, quality of care and perceptions of performance on competency evaluations. Existing literature inadequately describes how first-year resident conflict management styles evolve over time. The objective of this study is to assess if and how conflict management styles change during first year of paediatric residency in the United States. In 2021-2022, we conducted a non-experimental, longitudinal, survey study of first-year residents from 16 US-based paediatric residency programmes. Using the Thomas-Kilmann Conflict Mode Instrument, we scored first-year residents' use of five conflict management modes twice, 6 months apart. We calculated the percentage of first-year residents who experienced a change in predominant conflict management mode and assessed for changes in score and variance for each conflict management mode. Fifty-seven (18%) first-year residents participated in the first survey. Of those, 45 (14%) also completed the follow-up survey. Nonresponse bias analysis showed no significant difference in scores for early and late respondents or for second-survey respondents and non-respondents. Half of respondents experienced a change in predominant conflict management mode, but the distribution of predominant modes remained largely unchanged. When residents changed modes, they typically moved from one low-assertiveness mode, such as avoiding or accommodating, to the other. Only the use of the compromising conflict management mode significantly decreased. Variance did not significantly change. The overall lack of change in conflict management style may suggest the need for specific and focused educational interventions to help residents adjust their conflict handling strategies.