This paper presents a computational fluid dynamics study aimed at characterising the performance of swept tidal stream turbine blades. A prototypical straightbladed baseline design is selected from which multiple planforms are developed that incorporate backward curvature in their plane of rotation. Several parameters which define the curved blade geometry are investigated including the amount of sweep at the blade tip, the point at which the offset sweep begins, and the orientation of the blade’s aerofoil sections. The blades are characterised with respect to their energy capture and dominant loadings across their full operational range. It is found that backward sweep mostly reduces rotor thrust and root bending moments and leads to increased power capture at tip-speed ratios above peak power. However, most blades exhibited a decrease in peak power. These trends are increased by greater blade curvature - where more tip sweep exists or is more localised to the tip. It is found that station aerofoil alignment has a substantial impact on performance and argued that alignment to the tangential direction of travel produces the best performance.