Cardiovascular disease (CVD) is a major cause of death in Western societies. CVD risk is largely genetically determined. The molecular pathology is, however, not elucidated in a large number of families suffering from CVD. We applied exclusion linkage analysis and next-generation sequencing to elucidate the molecular defect underlying premature CVD in a small pedigree, comprising two generations of which six members suffered from premature CVD. A total of three variants showed co-segregation with the disease status in the family. Two of these variants were excluded from further analysis based on the prevalence in replication cohorts, whereas a non-synonymous variant in MCF.2 Cell Line Derived Transforming Sequence-like protein (MCF2L, c.2066A>G; p.(Asp689Gly); NM_001112732.1), located in the DH domain, was only present in the studied family. MCF2L is a guanine exchange factor that potentially links pathways that signal through Rac1 and RhoA. Indeed, in HeLa cells, MCF2L689Gly failed to activate Rac1 as well as RhoA, resulting in impaired stress fiber formation. Moreover, MCF2L protein was found in human atherosclerotic lesions but not in healthy tissue segments. In conclusion, a rare functional variant in MCF2L, leading to impaired DH function, was identified in a small pedigree with premature CVD. The presence of MCF2L in human atherosclerotic plaque specimen lends further support to its potential role in atherosclerosis.