This research was carried out in the experimental site of the Arid and Oasian cultures Laboratory of the Institute of Arid Regions, Medenine, Tunisia. It aims at studying the effects of compost on seed germination patterns, seedling growth, and plant development of muskmelon and tomato under greenhouse conditions. Three growth media were used: compost of date palm wastes and two reference media (peat and perlite). The results showed that compost presented a promising threshold of both maturity and stability, which is related to its neutral pH, C : N ratio, greater humic acid vs fulvic acid, and low values of chlorophyll-type compounds. Seeds of muskmelon and tomato germinated at varying liquid compost extract concentrations and muskmelon reached higher germination index values even at the pure extract solution (100%). Moreover, seeds of both species germinated relatively faster in peat than in compost and an overall delay in germination was observed, with a more pronounced reduction on tomato germination percentage. Produced seedlings have attained a similar vigour index among media (p <0.05). Compost of date palm was more suitable for muskmelon stem elongation and leaf-enlarging capacity than perlite. However, the gustative quality of fruits was not significantly affected by the medium-types. Thus, it is concluded the promoising effect of compost of date palm as potting medium and substrate in soilless culture under greenhouse conditions unless a pertinent choice of cultures.