Overweight and obesity at an early age are important criteria for predicting chronic diseases. Each anthropometric method available to assess obesity has its limitations. Recently, neck circumference (NC) has received greater attention as a new evaluation index. This study aimed to investigate the relationship between NC and overweight in Chinese Yi adolescents. A total of 647 Chinese Yi male and female students, aged 13–18 years, were randomly selected from a junior high school and a senior middle school in Leshan, Sichuan Province of China. The measurement indexes included height, weight, waist circumference (WC), and NC, and clinical information was collected by trained physicians. The neck cutoff values were determined through the receiver operating characteristic (ROC) curve and the area under the curve (AUC). The correlation among NC, body mass index (BMI), and WC was determined by Pearson's correlation coefficient. The ROC analysis revealed that the AUC values were 0.79–0.95 for boys and 0.83–0.91 for girls. The correlation among NC, BMI, and WC in obese boys and girls was higher than 0.70 in both genders. In addition, the NC cutoff values of high BMI ranged from 31.0 cm to 36.1 cm for boys and 31.2 cm to 34.5 cm for girls, respectively. There was a significant positive correlation between NC and obesity in Chinese Yi adolescents. The NC can be used as an additional index to predict the obesity of Chinese Yi adolescents.