• Urban sprawl in China is defined from six dimensions and represented by 18 measurements. • Data for 102 cities at county-level and above in Beijing-Tianjin-Hebei region are used to measure urban sprawl. • The spatial features of urban sprawl in small cities differ from those in large cities. • Small cities are facing an increasingly serious problem of urban sprawl. Urban sprawl has become a global phenomenon resulting in many critical social and environmental problems, but its characteristics and causes vary in different contexts, especially in developing countries such as China. Despite many studies on the urban growth of Chinese cities, not much is known about the county-level small cities. To better understand the dynamics of urban growth pattern across different sized cities, this study defined whether urban growth patterns are compactness or sprawl in each of six dimensions: land use efficiency, spatial pattern of urban land, inner structure of urban space, mixed uses, accessibility, and environmental impacts. Taking the 2 municipalities, 7 prefecture-level cities, and 93 county-level cities in Beijing-Tianjin-Hebei (BTH) region as cases, we assessed their urban growth patterns during 2015–2018. The results show that the regional policy on coordinated development of BTH region has promoted the growth of small cities, but these cities also tend to suffer from greater sprawl than larger cities. The differences of urban growth pattern between small and large cities exist in terms of the spatial pattern of urban land, inner structure of urban space, and environmental impacts. As small cities expand, they become spatially fragmented and decentralised. However, urban growth in larger cities has a greater negative impact on the natural environment. These findings suggest that we need to carefully consider the local context when developing urban growth management policies. [ABSTRACT FROM AUTHOR]