This paper describes the effect of Sn additions to PbMo6S8ribbons. These ribbons are produced via a vapor‐transport technique. Small amounts of Sn in Sn1−xPbxMo6S8alloy ribbons provide a significant (∼10×) increase inJcat high fields over that obtained with PbMo6S8alone. Critical current densities of 1×104A/cm2at 4.2 K near 20 T have been achieved for compositions withxnear 0.5. The lowJc’s in PbMo6S8appears to be related to the presence of a large fraction of a nonsuperconducting triclinic phase resulting from a partial phase transition at cryogenic temperatures. This phase transition is partially suppressed with Sn additions, resulting in an improved performance.