A novel hypoplastic constitutive model is proposed which accurately captures the geomechanical behavior of gas hydrate-bearing sediments. This model explicitly accounts for the effects of hydrate saturation, temperature, and pore pressure across different pore morphologies. A cementation coefficient ( ) is introduced which represents the influence of pore morphology on the sediment’s mechanical response. The predictive capabilities of the proposed model are thoroughly validated against an extensive dataset from the literature, covering various initial stress, hydrate saturation, and temperature conditions. The model’s generality is demonstrated by its ability to predict the mechanical behavior of sediments containing both methane ( ) and carbon dioxide ( ) hydrates. Furthermore, the model responses are validated using data obtained from testing natural hydrate cores from the Nankai Trough.