This paper presents the results of laboratory and field research on testing the use of phosphogypsum (PG) as a backfill material for construction projects. Laboratory evaluations indicate that the PG used in this study is not hazardous waste and meets the radioactive activity safety standards according to Vietnamese regulations. Raw PG did not meet the leachate requirements of QCVN 40:2011 – National technical regulation on industrial wastewater, thus it needs to be stabilized/solidified to mitigate contaminants. To assess the potential for leaching contaminants during actual use, the research team conducted field trials with two backfill sites using cement-stabilized PG, each with an area of 500 m2 and a compaction factor of K = 90: one with an HDPE liner and one without. Additionally, the team created a control site using traditional materials, with an area of 500 m2 and a compaction factor of K = 90, too. All test sites are equipped with groundwater monitoring wells to collect water samples for monitoring. The HDPE-lined site also featured a leachate collection pit. The sites were monitored, with groundwater, surface water and leachate collection pits observed over 18 months. Results from the observations show that when stabilized with a cement binder, phosphogypsum can meet the requirements for use as a backfill material for transportation infrastructure projects.