Objective To analyze the trends in relapse of Plasmodium vivax malaria in Dehong, Yunnan from 2014 to 2025, so as to provide insights into formulation of malaria control strategies. Methods A retrospective cross-sectional study was performed to analyze the trend of relapse rate of Plasmodium vivax. All data pertaining to reported P. vivax malaria cases in Dehong from 2014 to 2025 were extracted from the China Disease Control and Prevention Information System. Relapsed cases were verified with the duplicate checking function, and the relapse rate was calculated. Shapiro-Wilk test was used to test for normality and Levene’s test was used to test for homogeneity of variances. Independent-sample t-test was employed to compare the differences in relapse rates during the period between 2014-2019 and 2020-2025. In addition, the trends in the relapse rate were examined using interrupted time series (ITS) analysis with the intervention breakpoint of “switching to WHO-donated and Cyprus-produced primaquine for radical treatment of P. vivax and P. ovale malaria in Yunnan Province in 2020”. Results A total of 2 485 P. vivax malaria cases were reported in Dehong from 2014 to 2025, including 2 454 overseas imported cases (98.75%) and 79 relapsed cases, with an overall relapse rate of 3.18% (79/2 485). There was a significant difference in the relapse rate between 2020 and 2025 [(4.60 ± 1.82)%] and between 2014 and 2019 [(1.64 ± 1.40)%] (t = -3.158, P < 0.05), and an average increase of 2.96% [95% confidence interval (CI): 0.87% to 5.04%, P < 0.05] was seen in the relapse rate during the period from 2020 to 2025 relative to from 2014 to 2019. From 2014 to 2025, the vivax malaria relapse rate in Dehong fluctuated generally, and 2020 was an obvious breakpoint in the time series. ITS regression analysis revealed that the regression coefficients for the centering time variable, intervention variable, interaction term, and lagged variable were -0.363 (95% CI: -1.890 to 1.163; t = -0.582, P > 0.05), 5.115 (95% CI: -1.076 to 11.307; t = 2.021, P > 0.05), 0.078 (95% CI: -1.840 to 1.996; t = 0.099, P > 0.05), -0.069 (95% CI: -0.872 to 0.734; t = -0.210, P > 0.05), indicating a tendency towards a decline in the relapse rate of P. vivax malaria in Dehong during the period from 2014 to 2019 and from 2020 to 2025. In addition, the relapse rate exhibited an immediate increase at the intervention point in 2020, and the tendency towards a decline in the relapse rate slowed slightly after 2020. Conclusion The changing trends in the relapse rate of P. vivax malaria is not associated with the replacement of foreign countries-produced primaquine in Dehong. The relapse rate remains low, and there is no need to change the radical cure regimen. However, enhanced surveillance is required.