Yellowfin tuna (Thunnus albacares) is one of the important handline catches in Sabah, Malaysia. This study was carried out from January to December 2017 to determine the length-weight relationship and condition factor of yellowfin tuna in West Sabah waters, Malaysia. A total of 11,650 yellowfin tuna were sampled by enumerators at the landing site. The result showed that the length-weight relationship of this species was W=0.00003FL^2.8854 which exhibits negative allometry growth. Meanwhile, the mean relative condition factor (Kn) was 0.956±0.105 SE which the value is near to 1 indicating the fish is in good growth condition. This species is a commercially important type of tuna that can be found in tropical and subtropical seas across the globe. Therefore, it is crucial to understand the relationship between length and weight, as well as the relative condition factor. This information is essential for effective fishery resource management, ensuring the sustainability the long-term sustainability of fisheries resources.