In the current context of reduction of the available freshwater, drought is one of the most studied environmental constraints restricting plant growth. Many plant phenotyping platforms have been developed to assess plant responses to drought. In these high-throughput platforms, plants are grown in pots and soil water content is monitored automatically. Several studies have reported a major effect of pot size and soil volume on plant growth. The interaction of the pot size with other growth conditions is often ignored even when plant growth response to drought is studied. We investigated whether pot size affects shoot growth responses to drought. Shoot, leaf and cell traits were studied for three genotypes of oilseed rape (Brassica napus L.) grown under two soil water regimes, in small and in large pots. Small pots led to a reduction of all growth-related traits. These traits were also decreased in response to drought, whatever the genotype or the pot size but the trait sensitivity to drought depended on the pot size. Depending on traits, allometric relationships were modified by pot size demonstrating complex interactions between pot size and plant responses to drought. Our results suggest that pot size has to be considered when defining the experimental set up as it may affect plant responses to other environmental conditions.