The performance of nanofiltration (NF) with the addition of poly (acrylic acid) (PAA) for treatment of strontium-bearing nuclear wastewater was investigated using different NF membranes at various pH levels and PAA/Sr ratios. Greater Sr removal at elevated pH was attributed to the formation of SrCO3(s) due to the dissolution of atmospheric CO2. A substantial improvement in Sr removal was achieved with the addition of PAA that can make complexes with strontium ions and then be rejected by NF membranes. However, a rapid decrease in feed solution pH aggravated the fouling of a NF membrane, possibly because of the formation and the sorption of associated forms of PAA at the membrane surface.