Background Studies have revealed that guardians who sold their children for profit comprise the majority of child traffickers in China. Although sentencing disparity has been a focal topic in judicial studies, few scholars have investigated the influence of the guardian relationship on criminal sentencing for child trafficking. Objective The current study sought a better understanding of sentencing practices on child traffickers in China, focusing on the effects of the victim–offender relationship (VOR) and post-crime attitudes (PCAs) on sentencing outcomes. Participants and setting We retrieved all available sentencing documents related to “the trafficking of children” during the 2014–2016 period from China Judgments Online. The analytic dataset contained 844 child traffickers who were sentenced to a fixed term imprisonment. Methods A joint logistic and zero-truncated Poisson regression model was used to explore the main and interaction effects of VOR and PCAs on sentencing outcomes. Results Guardian offenders received sentences that were 12% shorter than those of non-guardians and were more likely to be given 60-month sentences, which is the minimum of the first statutory sentencing range. Guardian offenders who voluntarily surrendered also had a much higher chance of probation. The odds ratio of receiving probation for guardian offenders who surrendered was approximately three times higher than that of non-guardian offenders who did not surrender. Surrendering also reduced the sentence length of guardian offenders by 22%. Conclusions Shorter sentences and a higher chance of probation suggest that the Chinese judicial system considers child trafficking crimes involving guardians to be low harm offenses that pose little danger to society. However, this practice of leniency for cooperative guardian offenders offers offenders pragmatic ways to avoid incarceration, and does not help to solve the problems of guardian offenders who really want to give up custody of their children.