The movement and spreading of contaminated groundwater plumes and their mixing with non-contaminated water is strongly influenced by the heterogeneity of the aquifer properties, which may vary strongly over small spatial scales. Thus, imaging these small-scale features and monitoring transport of tracer plumes at a fine resolution is of interest to characterize transport processes in aquifers. Full-waveform inversion (FWI) of crosshole ground penetrating radar (GPR) measurements can provide an aquifer characterization at decimeter-scale resolution. The method produces images of both relative dielectric permittivity (ε_r) and bulk electrical conductivity (σ_b), which related to hydraulic aquifer properties and tracer distributions. To test the potential of time-lapse GPR FWI for imaging tracer plumes, we conducted a numerical experiment of tracer transport in a heterogeneous aquifer. Concentration was converted to saline and desalinated tracers, which changed σ_b, and to ethanol, which changed both ε_r and σ_b. The simulated ε_r and σ_b distributions in a crosshole plane were considered to simulate GPR data. These data were subsequently used to reconstruct ε_r and σ_b distributions using the crosshole 2D GPR FWI. Tracer concentrations were retrieved from the inverted ε_r and σ_b models using information about petrophysical parameters. GPR FWI ε_r images could recover preferential paths of ~0.2 m width, while the σ_b images resolved structures up to ~ 0.2-0.3 m. The results highlight that changes in ε_r, e.g., ethanol and hot water, can be used to image transport processes with high resolution by time-lapse GPR FWI, while the accuracy of the recovery of σ_b is limited.