A 1 year and 8 months old castrated male Pyrenean mountain dog was presented with an Achilles tendon rupture at least 5 weeks old. The defect between the two tendon ends was 2 cm in full extension of the tarsal joint. A new technique was successfully applied; a transposition and tenodesis of the fibularis brevis and fibularis longus muscles, combined with a 3 loop pulley suture and a tensor fascia lata graft. A transarticular external fixator was used for the first 3.5 weeks after surgery and a splint for the two following weeks. A 3 years follow-up shows the dog walking without any lameness.