Heavy metals are among the most critical environmental pollutants close to industrial areas. One example is the cultivated fields in the south of Alborz industrial city in Iran, which is irrigated by treated industrial wastewater. It is contaminated by heavy metals and irrigation with wastewater treatment plants effluent, which made it salty. In this study, the application of 2 amendments, biosolids and cow manure, in improving the heavy metal accumulation in the ornamental sunflower from these types of soils was investigated. A greenhouse experiment using a completely randomized design with 4 replications and applying cow manure and biosolids in 3 weight ratios (6%, 12%, 25%) was conducted to evaluate the efficiency of sunflower in removing Pb, Ni, and Zn from the soil. Adding the amendments increased the rate of germination by 50% to 176%. Although the simultaneous utilization of cow manure in high ratios with biosolids and cow manure with low biosolids decreased the sunflower survival, nonetheless, the simultaneous addition of these organic amendments could increase the survival rate in other treatments. Moreover, the plants’ biomass was increased by adding modifiers such as cow manure and biosolids. The results showed that in treatments with 2 modifiers, the remediation factor of Pb, Zn, and Ni has increased 83.7 to 95.5, 78.4 to 87.5, and 74.9 to 94.9, respectively, in comparison to the control one. Therefore, we conclude that adding biosolids and cow manure simultaneously could improve the ornamental sunflower ability to accumulate heavy metals.