The critical temperature of a triplet superconducting spin valve depends on the effectiveness of the conversion of singlet pairs in the superconductor to triplet pairs which can penetrate a ferromagnet and so drive a strong proximity effect. Here we compare the out‐of plane field dependence of the critical temperature in transition metal triplet spin valves with otherwise equivalent samples in which the singlet‐triplet converting spin mixer ferromagnet layer is omitted. We report a significant field‐dependent difference between the samples which is consistent with a magnetisation orientation dependent spin mixing efficiency in the spin valve.