Using Canadian plant‐level data, this paper shows that, depending on the industry, the differences in the average plant‐level productivity and cross‐plant allocation of resources between multi‐plant and single‐plant firms account for 1 to 15 per cent of the industry‐level TFP. A large part of this contribution stems from more efficient cross‐plant allocation of resources, measured by the covariance between plant size and productivity, in the pool of plants in multi‐plant firms compared to the pool of plants in single‐plant firms. There is less dispersion in the marginal products of the inputs, and thus less misallocation, in industries in which multi‐plant firms account for a larger share of output. The patterns found in the cross‐plant distribution of productivity and size are also consistent with better allocative efficiency among plants in multi‐plant firms than among plants in single‐plant firms.