Asymmetric cell divisions play an important role in development by producing daughter cells with different fates. They can also produce daughter cells of different sizes, but it is unclear whether these size differences contribute to cell fate decisions. Here, Richard Poole and colleagues carry out 4D-lineage analysis to demonstrate that the two cell divisions preceding DVC neuron formation in Caenorhabditis elegans embryos produce daughter cells of different sizes. Depleting known regulators of unequal cleavage can reduce the magnitude of these size differences, but this equalisation of daughter cell size has no effect on the expression of hlh-14, which encodes an essential transcription factor for DVC fate specification. Intriguingly, the authors find that depletion of hlh-14 itself can promote equalised cell cleavage in the DVC lineage. A forward genetic screen identifies let-19 as an upstream regulator of hlh-14, and depletion of let-19 leads to loss of hlh-14 expression, as well as to the equalisation of daughter cell size within the DVC lineage. Overall, this work suggests that unequal cleavage does not significantly influence cell fate in the DVC lineage. Instead, the authors suggest that embryonic neuroblast cell size is regulated by the same transcriptional mechanisms that regulate neuronal fate acquisition, via the control of unequal cell divisions.