Fruit size, shape and colour are important determinants of fruit quality in tomato. Among the different genetic factors, the OVATEgene is a key regulator of fruit elongation in tomato. The loss-of-function recessive ovateallele results from a functional single nucleotide polymorphism (SNP) in the second exon of the gene to produce fruit elongation and variable fruit shapes in different genetic backgrounds. The mutation has also been associated with increased fruit firmness, a desirable trait for processing purpose of tomato. However, the recessive nature of this important mutant allele makes its identification and utilization in breeding programme difficult. Hence, we developed the OVATEgene-based functional marker using the tetra-primer amplification refractory mutation system (T-ARMS) strategy. The developed functional marker was capable of identifying the allelic status at OVATElocus in a co-dominant manner, using routine polymerase chain reaction (PCR) followed by standard agarose gel electrophoresis. Trait–marker association of the developed functional marker was validated in the F2segregants bearing elongated and non-elongated fruits. Thus, the functional marker developed and validated in this study will assist the tomato breeders in identification and introgression of the desired allelic version of the OVATEgene in a time-, labour- and cost-effective manner. Moreover, identification of the allelic status at the OVATElocus will help in exploring its interacting partners and modifiers for detailed understanding of the fascinating genetics behind fruit shape variation in tomato.