Background: Micro- and nanoplastics (MNPs) are widespread environmental contaminants with growing evidence linking them to adverse health effects, including progression and worsening of allergic diseases. As allergies are rapidly increasing among youth (affecting almost 30% of children), this demographic represents a vulnerable population facing emerging environmental threats. Since no prior study has investigated MNP risks perceptions in an allergic population, this study aimed to assess public awareness and risk perception of MNP in Croatian youth, focusing on the influence of urbanicity, education, and allergy status. Methods: A total of 1155 participants (aged 6–18 years) were recruited from three Croatian regions as part of the EU Horizon 2020 IMPTOX and the Horizon Europe EDIAQI studies. Allergy status was determined via skin prick tests (SPT), and standardized questionnaires were used to collect data on MNP awareness and perception. Results: Awareness was significantly higher among allergic individuals (89.5% vs. non-allergic 79%, FDR p value= 0.036) and those with university-level education (88.3% vs. elementary 63.3%, FDR p value = 0.050). Allergic participants were also more concerned about food contamination by MNPs (87.7%) compared to non-allergic individuals (79.2%), FDR p value = 0.005). Media and social media were the primary sources of information regarding MNPs (FDR p value = 0.026). Conclusions: Education and allergy status are the strongest predictors of MNP awareness and related risk perceptions in the Croatian population. Targeted public health communication and educational strategies are needed to translate basic awareness into informed behavioral and policy engagement.