Objective The Kruppel-like factor 11 (KLF11) gene causes maturity-onset diabetes of the young 7 (MODY7). There are few reports on the clinical and functional characteristics of KLF11 mutations in patients with MODY7, making diagnosis and treatment complicated. Research Design and Methods We report a novel KLF11 variant associated with MODY7 in a Chinese family. The proband had hyperglycemia at 9 years of age, and his mother had developed diabetes at age 28 years. Both required insulin injections from the initial phase of the disease. They were negative for islet cell autoantibodies and had normal fasting C-peptide levels. We observed changes in the levels of fasting blood glucose, C-peptide, and islet cell autoantibodies in the proband over 4.5 years. Results Whole-exon sequencing was used to screen the proband and his family members for KLF11 variants. The heterozygous KLF11 variant (c.1045C>T, p. Pro349Ser) was identified in the proband, his mother, his maternal grandmother, and an elderly aunt, although the latter two individuals were unaffected. In silico analyses indicated that this variant involved a change in the amino acid side chain in the transcriptional regulatory domain 3. Luciferase reporter assays revealed that the variant had impaired insulin promoter regulation activity. Moreover, in vitro analyses showed that this variant impaired insulin secretion from pancreatic beta cells. Conclusions This study documents a novel heterozygous KLF11 variant (p. Pro349Ser) as a potential monogenic mutation associated with MODY7 in a family. This variant impairs insulin secretion from pancreatic beta cells, possibly by repressing insulin promoter regulation activity.