BRCA mutations are the main known hereditary factors for ovarian cancer. Notably, emerging evidence has led to considerable interest in the role of sirtuin 1 (SIRT1) in ovarian cancer development. However, dynamic crosstalk between BRCA1 and SIRT1 is poorly understood. Here, we showed that: (i) BRCA1 inactivation events (mutation, promoter methylation, or knockdown) were accompanied by decreased SIRT1 levels and increased nicotinamide adenine dinucleotide (NAD) levels and a subsequent increase in SIRT1 activity; (ii) overexpression of BRCA1 resulted in increased SIRT1 levels, an impairment in NAD synthesis, and a subsequent inhibition of SIRT1 activity; and (iii) intracellular NAD levels were largely responsible for regulating SIRT1 activity, and BRCA1 expression patterns correlated with SIRT1 levels and NAD levels correlated with SIRT1 activity in human ovarian cancer specimens. Interestingly, although BRCA1 inactivation events inhibited SIRT1 expression, they led to a substantial increase in NAD levels that enhanced NAD-related SIRT1 activity. This is a special BRCA1-mediated compensatory mechanism for the maintenance of SIRT1 function. Therefore, these results highlight a novel interaction between BRCA1 and SIRT1, which may be beneficial for the dynamic balance between BRCA1-related biologic processes and SIRT1-related energy metabolism and stress response.