Antarctic fish of the suborder Notothenioidei display remarkable metabolic adaptations to life in the Southern Ocean. These comprise very low, energy saving metabolic rates, higher mitochondrial densities, cold adapted enzymes, anti-freeze proteins and last but not least, the loss of hemoglobin in the icefishes (family Channichthyidae). Yet, those adaptations come at a premium and render Antarctic notothenioids especially vulnerable to a warming ocean. As the central players in aerobic energy metabolism, mitochondria and their acclimatory plasticity play an important role in buffering the effects of climate change and much depends on their thermal stability and acclimatory capacity. I will present an overview of my studies on notothenioid mitochondria under acute and chronic thermal exposure and explore the differences in thermal reaction norms, leak rates and thermal stability of the individual respiratory complexes in Antarctic nototheniids (N. rossii, N. coriiceps), trematomids (T. eulepidotus, T. loennbergii) and channichthyids (C. hamatus, C. wilsoni) and contrast them to Austral nototheniids (N. angustata) as well as Arctic and temperate gadoids.