Ataxia‐telangiectasia (A‐T) is a genetic disease, associated with progressive motor impairment and a lack of functional ATM protein. It has been reported that immunoreactive tyrosine hydroxylase and dopamine transporter are reduced in an Atm^–/– mouse model of A‐T. These observations led to a hypothesis that A‐T is associated with loss of nigrostriatal dopamine and prompted the launch of clinical trials to evaluate a therapeutic utility of the anti‐parkinsonian drug, l‐DOPA. To test for dopamine depletion more directly, we measured regional levels of monoamines and their metabolites in the Atm^–/– mouse brain. We also measured levels of NAD⁺, a cofactor for dopamine biosynthesis and substrate of the DNA damage surveillance enzyme, poly(ADP‐ribose) polymerase (PARP). Constitutive activation of PARP has been posited to cause NAD⁺ depletion. We observed no reduction in monoamine transmitters and no depletion of NAD⁺, or other high energy phosphate donors in the adult Atm^–/– cerebellum, striatum, or ventral mesencephalon. However, our studies did reveal a progressive sensorimotor impairment in Atm^–/– mice that may serve as a relevant proxy for progressive neurological impairment in the human disease. Our results call into question the involvement of dopamine in A‐T and the therapeutic strategy of enhancing dopaminergic function with l‐DOPA.