ESR1 has been listed in the Human Obesity Gene Map as candidate gene associated with obesity. Thus, in this study, we investigated the effect of the ESR1 rs1884051 polymorphism on obesity-related variables, together with their modulations by dietary intake in Korean men. The obesity-related variables and dietary intake of 3,039 Korean men aged 40-59 years from KoGES database were analyzed. Body weight (P = 0.007), BMI (P = 0.003), waist-hip ratio (= 0.011), fat body mass (P = 0.010), and body fat percentage (P = 0.040) were significantly lower in subjects with the minor T allele of ESR1 rs1884051 than in subjects carrying the C allele. Moreover, the rs1884051 T allele was associated with a decreased risk of obesity prevalence (P = 0.040). Among the subjects whose total energy intake was below the median, carrier of the minor T allele of ESR1 rs1884051 had a lower BMI (P = 0.003) when compared with subjects carrying the C allele. In addition, among subjects whose plant protein intake was above the median, carrier of the minor T allele of ESR1 rs1884051 had a lower BMI (P = 0.044) compared with subjects carrying the C allele. Our findings demonstrate that there is a significant association between the ESR1 rs1884051 variant and obesity-related variables and this association can be potentially modified by dietary energy and plant protein intake.