The first aim of this study was to examine the prevalence of below average gross motor skills in a representative sample of US children aged 3 to 5 years. The second aim was to identify socioeconomic and familial characteristics that are associated with below average gross motor skills. Secondary analysis was conducted using the datasets from the 2012 National Health and Examination Survey National Youth Fitness Survey (NNYFS). The NNYFS assessed gross motor skills among 329 children aged 3-5 years, using the Test of Gross Motor Development-Second Edition (TGMD-2). Socioeconomic and familial characteristics of interest, such as family income and family structure, were asked in an in-person interview. This study estimated that one in three US children age 3 to 5 years old (33.9%) scored below average for gross motor quotient. In the gross motor subsets, one in four (24.4%) scored below average for locomotion and two in five (39.9%) scored below average for object control. Children living below the poverty threshold were more likely to have a higher gross motor quotient (odds ratio, OR = 2.76; 95% confidence interval, CI = 1.09-7.00). Girls were more likely to have a higher locomotor score (OR = 2.17; 95% CI = 1.10-4.25). Those living with other child(ren) aged ≤5 years were more likely to have a higher locomotor score (OR = 2.36; 95% CI = 1.01-5.54), while those living with child(ren) aged 6-17 years were more likely to have a higher object control score (OR = 1.83; 95% CI = 1.24-2.69). This study revealed risk factors associated with poor gross motor development, furthering our understanding of gross motor development in early childhood.