Abstract: Clerodendrum trichotomum Thunb. is a broadleaved understory shrub, well recognized for the ecological and economic values, such as ecological restoration and medical use. However, this species is relatively poorly characterized regarding the seedling growth in natural populations or under controlled conditions. Our study aimed to fill this gap by examining both the phenotypic and growth parameters of seedlings in response to a series of light intensity (i.e. 100%, 20% and 5% sunlight) and soil water content (i.e. 75%—100%, 50%—75%, 25%—50% field capacity). The results revealed that most of seedling morphological features were more likely to be influenced by light intensity rather than soil water content. However, these phenotypic and growth parameters varied in response to light intensity. Some specifically, stem height, stem diameter, root biomass ratio, relative growth rate and net assimilation rate exhibited a positive correlation with light intensity particular for the latter two indicators, while stem biomass ratio, leaf biomass ratio, mean leaf area ratio and specific leaf area showed the reverse trend. Under 20% of full light intensity, seedlings presented shadetolerance through large increase of mean leaf area ratio; While the mean relative growth rate under three soil water content was extremely low under 5% of full light intensity only accounting for 8.2% and 11.4% of that under 100% and 20% of full light intensity respectively, which probably indicated seedling growth would be severely hampered by deep shade.