Bergmann’s Rule is an ecogeographical trend describing the tendency in body size to increase towards higher elevations and either high-latitude extreme. This pattern is well-supported intraspecifically in endotherms and is often explained by an underlying negative body size-temperature relationship, driven by heat conservation in colder environments. In contrast, at broader taxonomic scales (i.e., interspecific evaluations) and within ectotherms, evaluations of Bergmann’s Rule yield conflicting results. Proposed mechanisms facilitating body size-latitude trends in ectotherms are also more varied, including increased longevity at higher latitudes and cell size variation induced by temperature. Body shape modifications in the surface area to volume ratio may drive the frequently observed positive body size-latitude relationship in endotherms, but body shape variation across latitude has not been well-evaluated in ectotherms. Moreover, body shape is indicative of locomotion, trophic niche, and/or thermoregulatory performance, and selective pressures on these complex traits may systematically differ with latitude. We therefore looked for trends in size and shape associated with latitude and water depth, across 3194 marine species (266 families; 35 orders) of teleost fishes, using a rigorous phylogenetic comparative approach. Shape variables were constructed from linear morphometric measurements of length, depth, and width. Our analyses reveal that shape, but not size, changes systematically with latitude across the full teleost dataset. At higher latitudes fishes are more elongate and wider. A latitudinal cline in fish body shape suggests that body size trends observed in other taxa may only serve as correlates for selective gradients on other morphological features.