Pollution stands as a major factor affecting wildlife populations, with amphibians being an exceptionally vulnerable group. Plastic pollution, particularly nanoplastics (NPs) stemming from primary and secondary sources, garners traction owing to its distinctive characteristics, including its minute size, large surface area, and heightened surface reactivity. As the demand for more sustainable alternatives to conventional plastics intensifies, the emergence of Polyhydroxybutyrate (PHB) as a novel bio-based and biodegradable plastic stands out. However, the understanding of its environmental impact, particularly regarding its nanosized particles, remains limited. These particles possess the potential to exert pernicious effects and act as carriers for environmental contaminants into biota. Sertraline, one of the most consumed antidepressants, is expected to be present in the aquatic environment due to patient excretion, inefficient wastewater treatment, and improper disposal. Given its bioactive nature, even low concentrations of sertraline may pose undesirable effects on biota. The objectives of this work were to assess the hazards of PHB nanoplastics and sertraline, in single and combined exposure, towards two aquatic early life stages of the model organism Xenopus laevis. Additionally, in vitro assays were conducted to understand the suitability of two cell lines as non-animal alternatives to be used in first tiers of environmental risk assessment for this type of contamination. Our results suggested high tadpole sensitivity to sertraline (96-h LC₅₀: 449.81 µg L^-1), when compared to embryos (96-h LC₅₀: 2.58 mg L^-1), while PHB-NPs did not show statistically differences in the monitored parameters, however NPs may exert modulatory effects in mixture with sertraline.