In arid and semiarid regions such as Niger, irrigated agriculture leads to soil salinization, particularly through irrigation water salts, and has adverse effects on crop production such as vegetable crops including onion. The main objective of this study, conducted in the experimental site of Djibo Hamani University of Tahoua in Niger, was to evaluate the effects of organic fertilizer on the growth and yield of onion crops irrigated with saline water. The experiment was performed in split-plot design to test tree type of fertilizer (chemical fertilizer, compost and millet glumes) and four (04) levels of irrigation water salinity in electrical conductivity values (ECw) (S0 = 0.28 dS/m as control, S1 = 2 dS/m, S2 = 4 dS/m and S3 = 6 dS/m). The growth parameters and bulb yield were evaluated during 4 months of onion cropping season. The results showed that the use of irrigation saline water significantly decreased the growth and bulb yield of onion crops. The yield in onion bulbs is 1.55 to 3.94 times higher with control (0.28 dS/m) than that with high saline water (ECw = 6 dS/m). Compared to control in irrigation water, the reduction in fresh onion bulb yield was 38.8, 52.6 and 63.5% respectively for ECw of 2, 4 and 6 dS/m. Furthermore, the application of organic fertilizers, particularly compost, improves salt-tolerance of onion crops in order to promote growth and bulb yield. Indeed, when irrigating onion crops with saline water (ECw of 2, 4 and 6 dS/m), the onion bulb yield is significantly higher under compost than under chemical fertilizer and glumes. At high irrigation saline water (ECw = 6 dS/m), the yield in onion bulbs is 1.9 and 2.1 times higher under compost than that under chemical fertilizer and glumes respectively. Thus, the compost is the promising organic amendment in a semiarid region of Tahoua in Niger to