Pile jacking technology allows displacement piles to be installed without noise and vibration. The ‘press-in’ method of pile jacking uses previously-installed piles for reaction, so the piles must be installed at close centres. Axial load tests have been conducted to investigate whether existing design guidance based on driven and bored pile behaviour can be applied to closely-spaced jacked piles. The observed axial response was notably stiff, and failure was reached at a load equal to the installation force. This high stiffness is attributed to pre-loading of the pile base during installation and the presence of residual base load. Load transfer back-analysis was used to establish simple parameters for the modelling of single pile stiffness. These parameters predicted the pile group response well using elastic superposition to account for interaction. This high stiffness could lead to more efficient design if jacked piles are used.