Abstract Sea lettuce (Ulva rigida) is an underutilized green macroalga. Scant knowledge and understanding exist regarding the optimal processing technologies to maximize seaweed nutrition. Pretreatment of sea lettuce before drying, either by blanching or steaming, induced diverse physical and biological property changes. Greenness increased, while lightness of the-sea lettuce reduced. Both drying processes reduced textural parameters and impacted sea lettuce bioactivity, with increased antioxidant capacity and phenolic compound content. Steaming followed by oven drying at 60 °C for 2.30 h maintained bioactivities during 4 months of storage. Food processing increased the ease of consumption and also maintained the nutritional value of the sea lettuce, thereby promoting the utilization of this seaweed as a beneficial food ingredient.