Silver nanospheres were transformed into triangular nanoprisms and nanodisks via a photoinduced growth process. In order to show the citrate ion concentration effect, the silver nanospheres were prepared in three different silver/citrate ratios (1:1, 1:2 and 1:3). The photoinduced shape transformation was carried out under magnetic or ultrasonic stirring with the purpose of showing the stirring effect. Scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) images of the obtained nanoplates show nanoprisms and nanodisks of 50 and 30 nm, respectively. The formation of silver nanoplates is very sensitive to the citrate ion concentration, which is confirmed by the UV-Vis spectra. Higher concentrations of citrate ion produce triangular nanoprisms with more sharp vertices. The ultrasonic stirring limits and controls the nanoplate growth.