The papaya (Carica papaya L.) is among the mainly fruit species produced in tropical and subtropical climate. The salinity of water in agricultural areas is considered a limiting factor for the expansion of papaya. This study aimed to evaluate calcium-enriched microalgae extract (EMa-Ca) as an attenuator of saline stress in irrigation water on the growth and physiology of Formosa papaya seedlings, hybrid Tainung. The experiment was conducted in a protected environment, with treatments distributed in a 5 × 2 factorial scheme, comprising five electrical conductivities of irrigation water (0.50; 1.10; 2.50; 3.90 and 4.50 dSm-1) with the presence and absence of EMa-Ca in the substrate. Evaluated characteristics were: plant height, number of leaves, stem diameter, leaf area, dry masses weight of roots, aboveground parts and total. Gas exchanges and chlorophyll indices (a, b and total) were also evaluated. The application of EMa-Ca resulted in an increase of 6.05% in height and 6.33% in trunk diameter. The number of leaves decreased with an increase in electrical conductivity, and the leaf area was reduced by 33%. All seedling dry masses showed greater declines in the absence of EM-Ca. The EMa-Ca increased net photosynthesis, CO2 concentration, transpiration and stomatal conductance by 39.13%, 30.43%, 38.88% and 42.85%, respectively. For chlorophyll without the use of EMa-Ca, a decrease rate of 1.21%, 0.41% and 1.62% was observed for Chla, Chlb and Chlt, respectively. Therefore, the EMa-Ca application (1.0 ml/L) significantly enhance the vegetative development, gas exchanges, and chlorophyll indices of papaya seedlings under saline stress conditions.