Tomato leaf mould disease is a serious foliar disease caused by Cladosporium fulvum, resulting in a significant reduction in yield and quality, especially under protected cultivation. Finding new resistant genes against leaf mould has become one of the important goals of tomato breeding. Cf‐12‐tomato showed good resistance to several C. fulvum races. The Cf‐12 was mapped using re‐sequencing and BSA methods. Allelism test for Cf‐12, Cf‐5 and Cf‐9 was performed. The results showed that Cf‐12 is an independently assigned C. fulvum resistance gene. About 67,853 high‐quality polymorphic SNPs were found and 233 genes were annotated in three associated regions of 5.85 Mb on Chr. 6s. Three genes with typical Cf‐type characters encoding the leucine‐rich repeat receptor‐like protein were screened out. Using qRT‐PCR, structural and phylogenetic analysis, only the Solyc06g008265.1.1‐CGN7495 was finally identified. An effective InDel marker, InD‐3F/1R, was designed for MAS breeding. Our research provides new insights into the mapping of the Cf‐12, and provides a basis for Cf‐12 cloning and the Cf genetic evolution analysis.