While the induction of teratology by cadmium (Cd) on diatoms is already known, reversal kinetics are not well documented. This study aims to understand the viability of diatoms exhibiting teratological frustules and their reproduction capacities within a Cd-impacted population to predict their return to normal diatom forms. We worked on a frequently encountered species in French hydrosystems: Planothidium frequentissimum (Lange-Bertalot) Round & L. Bukhtiyarova. First, a 21-d contamination phase highlighted increasing inductionof different teratological types in response to two levels of Cd contamination: 20 and 100 μg · L−1. The deformity counting indicated that Cd firstly generated striae and mixed teratologies, then affected the central area and the valves. Second, a 28-d decontamination phase demonstrated the Cd depuration capacity of Planothidium frequentissimum. Cd half-lives appeared relatively low, ~6 d for the 100 μg · L−1 condition. Moreover, the decontamination phase showed a decrease in teratology abundances, but a still incomplete recovery after 28 d. Deformations of the striae appeared to be the most sustainable phenotype since they were still significantly higher than in reference cultures at the end of the decontamination phase for both Cd cultures.