The initiation of tomato fruit growth, fruit set, is very sensitive to environmental conditions. Therefore, an understanding of the mechanisms that regulate this process can facilitate the production of this agriculturally valuable fruit crop. Over the years, it has been well established that tomato fruit set depends on successful pollination and fertilization, which trigger the fruit developmental programme through the activation of the auxin and gibberellin signalling pathways. However, the exact role of each of these two hormones is still poorly understood, probably because only few of the signalling components involved have been identified so far. Recent research on fruit set induced by hormone applications has led to new insights into hormone biosynthesis and signalling. The aim of this review is to consolidate the current knowledge on the role of auxin and gibberellin in tomato fruit set.