Ubiquinol cytochrome c reductase hinge protein (UQCRH) is required for the electron transfer between cytochrome c₁ and c of the mitochondrial cytochrome bc₁ Complex (CIII). A two-exon deletion in the human UQCRH gene has recently been identified as the cause for a rare familial mitochondrial disorder. Deletion of the corresponding gene in the mouse (Uqcrh-KO) resulted in similar biochemical and clinical defects including impairment of CIII, failure to thrive, elevated blood glucose levels, and early death. Here, we set out to test how global ablation of the murine Uqcrh affects cardiac morphology, contractility, and bioenergetics. Hearts from Uqcrh-KO mutant mice were macroscopically smaller compared to wildtype littermate controls despite similar geometries as observed by transthoracic echocardiography (TTE). Relating TTE-assessed heart morphology to body mass revealed the development of subtle cardiac oversize, but histopathological analysis showed no excess collagen deposition. Nonetheless, Uqcrh-KO hearts developed pronounced contractile dysfunction. To assess mitochondrial functions, we used a newly developed high-resolution respirometer NextGen-O2k to monitoring mitochondrial respiratory capacity simultaneously with ETS-reactive Q-redox state or production of reactive oxygen species (ROS). Compared to wildtype littermate controls, mitochondrial respiratory capacity was decreased and Q more reduced in Uqcrh-KO, indicative of an impaired respiratory electron transfer system (ETS). Yet, mitochondrial ROS production was not increased. Taken together, our data suggest that Uqcrh-KO leads to cardiac contractile dysfunction at 9 weeks of age, which is associated with impaired bioenergetics but not with mitochondrial ROS production.